Stress-Relaxed AlN-Buffer-Oriented GaN-Nano-Obelisks-Based High-Performance UV Photodetector
Round 1
Reviewer 1 Report
In this manuscript, the authors demonstrated GaN UV photodetectors by growing GaN/AlN heterostructures on Si by MBE. The authors tried different growth conditions for optimizing epilayer quality and strain relaxation properties on Si substrate. The manuscript is generally well written, and I suggest the authors reflect below points for publication.
(1) The authors showed 2theta-omega scan to show that (0001) nitride is grown. However, the SEM morphologies suggest that there could be severe in-plane rotations. Given that GaN nanostructures are not aligned with each other, I think it is plausible that the structure is single-crystal only along out-of-plane direction, but not in-plane. Therefore, the authors need to present in-plane crystallinity of the grown film, for example by XRD phi-scan.
(2) Calculating strain relaxation from 2theta-omega is prone to error, since film’s mosaicity can also affect the peak position. The authors could conduct XRD-RSM mapping or Raman spectra measurement to corroborate their claims.
(3) I suggest changing responsivity unit of mA/W to A/W.
Author Response
Response to the Reviewer-1
The manuscript entitled "Stress Relaxed AlN Buffer Oriented GaN-Nano-Obelisks based High-Performance UV-Photodetector" Electronic Materials - Research Article, No. Electronicment-2053832.
We would like to express our gratitude and appreciation to the reviewer for the thorough review of our manuscript and the valuable comments and suggestions to improve our manuscript. We have addressed all the concerns raised by the reviewer, and a point-by-point response is given below. The manuscript is revised accordingly, and the revisions are highlighted in red.
General Comment: In this manuscript, the authors demonstrated GaN UV photodetectors by growing GaN/AlN heterostructures on Si by MBE. The authors tried different growth conditions for optimizing epilayer quality and strain relaxation properties on Si substrate. The manuscript is generally well written, and I suggest the authors reflect below points for publication.
Author Response: We would like to thank the learned reviewer for reviewing our manuscript and giving a positive response to improve the manuscript. We have revised the manuscript and addressed all the concerns raised by the reviewer in detail.
Comment: 1: The authors showed 2theta-omega scan to show that (0001) nitride is grown. However, the SEM morphologies suggest that there could be severe in-plane rotations. Given that GaN nanostructures are not aligned with each other, I think it is plausible that the structure is single-crystal only along out-of-plane direction, but not in-plane. Therefore, the authors need to present in-plane crystallinity of the grown film, for example by XRD phi-scan.
Author Response: We really appreciate the diligent reading of the learned reviewer and insightful comments. To confirm the in-plane crystallinity of the grown film, an HRXRD 2theta-omega symmetric scan has been attached for better understanding.
Figure 1: High-resolution X-ray diffractogram display rocking curve omega scan along symmetric diffraction plane.
Comment: 2: Calculating strain relaxation from 2theta-omega is prone to error, since film’s mosaicity can also affect the peak position. The authors could conduct XRD-RSM mapping or Raman spectra measurement to corroborate their claims.
Author Response: We would like to thank the learned reviewer for this insightful comment. We completely agree that the strain calculated by the HRXRD 2 theta-omega scan could have some error. In the present work, the position of the silicon peak was optimized by HRXRD measurements to avoid errors in the obtained data. Moreover, the Raman measurement was carried out for the stress calculation and obtained Raman modes were used to classify the wurtzite structure of GaN. The E2 mode of strain-free GaN is known to be 567.6 ± 0.1 cm–1 at room temperature. In figure 2, the peak values are positioned at ~566.78, ~565.63, & ~565.16 cm-1 of E2 (high) mode for the grown films nO, nP & nW sample, respectively. The calculated stress was found to be 0.19 GPa, 0.45, and 0.56 GPa for sample nO, nP, and nW, respectively. However, we have already discussed the Raman analysis of the heterostructures in our earlier reports. Therefore we are not added to the main manuscript.
Figure 2: Raman spectra of GaN films grown by PAMBE on Silicon substrate with an inserted variation of peak value and FWHM of GaN E2 (H) mode for all three samples.
Comment: 3: I suggest changing responsivity unit of mA/W to A/W.
Author Response: Thank you for your careful reading. We have replaced "mA/W" with " A/W " throughout the manuscript.
Finally, we sincerely thank the reviewer for the careful evaluation and constructive comments to improve the manuscript. Hopefully, the response and the revised manuscript will be acceptable and will accept this work for publication in “Electronic Materials.”
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript focuses on the effects of AlN buffer layer deposition temperature on the micro-structure control of the epitaxially grown GaN. In optical devices, the morphology of the active layer is crucial as that impacts the light-matter interactions, confirming the importance of this study. The experimental methods are nicely explained, particularly the growth process schematic shown in Figure 1 that will help readers follow the process and even replicate the experiments independently. Several techniques were used to study the morphology of the GaN/AlN/Si heterostructures and their optoelectronic properties were characterized. Although the reasoning for improved PL and photodetector performance of nano-obelisk is explained by the strain-relaxation provided by a lower growth temperature of the buffer AlN layer, there are some aspects of the results which raise doubt over this argument. It is recommended that authors make necessary edits to resolve this confusion in a revised version.
1. As explained in the discussion of Figure 2 on XRD, AlN films have biaxial strain that depends on the growth temperature. Although this concept is plausible, the XRD data itself does not seem accurate. If you consider the substrate Si (111) itself, all three XRD plots have a shift in the peak position going towards a lower 2-theta value from a to c. Is there a difference in measurement technique or how the detectors are aligned to the substrate peak? Such a shift could also impact the peak positions of AlN, which is later used to calculate strain. Explain in the paper, how does this impact the shift in the AlN peak that is used to calculate the strain? Suggest repeating the XRD measurements to confirm the peak shifts, if any.
2. If the XRD data is correct, then since there is a growth temperature-dependence of lattice constant of AlN, could deposition at temperatures <770C provide even lower strain? Why is the study limited to 770C-830C?
3. Further, it is suggested to include the XRD data for only the AlN buffer layer grown on Si (111) without the GaN layer to fully understand the strain in the AlN itself, and how it is impacted by the growth temperature. Also include SEM images of the AlN buffer layer, to understand how the growth temperature impacts its morphology, and if it has any surface templating effect on the GaN morphology.
4. In lines 134-137, it is mentioned that reduced strain leads to "better AlN growth", and later "deteriorated quality...". The use of "better" and "deteriorated" is unclear, since the optoelectronic performance of films with higher strain is still similar, and not significantly worse than nano-obelisk.
5. The legends and the plots in Figure 3b-d have GL and RL bands mixed up, making it difficult to follow the explanation. The discussion in lines 181-185 and the Table 1, shows that YL peak is the least for nO while and RL is highest. Does that indicate there are more defects in nO, than nW even if nO has reduced strain? Suggest clarifying these figures and the related discussion.
6. In order to better understand the explanation given through SEM images, it is suggested to include a lower magnification image, as it is critical to see the overall surface morphology across a larger sample area. In lines 201-204, the use of "significantly compact domains and finer structures" must be backed by statistical image analysis comparing grain size. Moreover, in Figure 4a for nO, clear size variation is visible where finer structures are surrounding giant grains, which are even larger than those observed in nW. Looking at the image suggests that overall nP have the most compact grains on average, and nO morphology is the most inconsistent across the imaged area, which is opposite to the explanation given in lines 201-204.
7. Kindly explain the significance of the layered structure observed in Figure 4a. Perhaps it is the layered growth features in the nO that result in better PD performance? Other structures do not seem to have these stacked-layer nano-structuring in the grains.
8. Additional analysis would help clarify the observations from the SEM image. First, comparing the FWHM of the GaN and AlN XRD peaks to get the information on crystallize size. Secondly, either an oblique-view SEM or AFM would help support the claim of nO and nP forming "tower-like structures, which leads to larger surface area" in lines 198-199. Finally, EBSD analysis will provide detailed information on the crystalline orientation and strain distribution.
9. The comparison of the switching speed of the various morphology is not clear from the plots. So, to make it easier for a reader to observe these differences, it will help if a separate plot is added where the peaks for various morphology are overlaid together. For instance, a normalized Iph plot of a single pulse for a given bias, could enable easier understanding of the peak rise and decay time.
10. Suggest adding to the methods section, details of the film thickness for both AlN buffer and GaN layers.
Here are some additional suggestions to improve the reading experience of the journal audience:
A. This work is similar to the author's previous paper Ref #6 where the effect of AlN buffer layer growth temperature was studied for the properties of AlGaN. It is suggested that a few lines be added in the introduction to explain the findings of Ref #6 and how this manuscript builds on to the prior work.
B. The Introduction section must make it clear as to why a larger aspect ratio morphology is preferred over other microstructures.
C. A majority of the references, especially in the Introduction section are self-citations and do not capture the whole body of research conducted by the community. Also, an unpublished work cannot be included as a reference, unless it is made public as pre-prints. Relevant references must be added in this manuscript.
D. There are some sentences, lines 46-49, 53-55, which are confusing and self-contradictory to the work carried out.
Author Response
Response to the Reviewer-2
The manuscript entitled "Stress Relaxed AlN Buffer Oriented GaN-Nano-Obelisks based High-Performance UV-Photodetector" Electronic Materials - Research Article, No. Electronicment-2053832.
We would like to express our gratitude and appreciation to the reviewer for the thorough review of our manuscript and the valuable comments and suggestions to improve our manuscript. We have addressed all the concerns raised by the reviewer, and a point-by-point response is given below. The manuscript is revised accordingly, and the revisions are highlighted in red.
General Comment: The manuscript focuses on the effects of AlN buffer layer deposition temperature on the micro-structure control of the epitaxially grown GaN. In optical devices, the morphology of the active layer is crucial as that impacts the light-matter interactions, confirming the importance of this study. The experimental methods are nicely explained, particularly the growth process schematic shown in Figure 1 that will help readers follow the process and even replicate the experiments independently. Several techniques were used to study the morphology of the GaN/AlN/Si heterostructures and their optoelectronic properties were characterized. Although the reasoning for improved PL and photodetector performance of nano-obelisk is explained by the strain-relaxation provided by a lower growth temperature of the buffer AlN layer, there are some aspects of the results which raise doubt over this argument. It is recommended that authors make necessary edits to resolve this confusion in a revised version.
Author Response: We appreciate the learned reviewer for positive and insightful comments for improving the manuscript. We have addressed all the concerns in the revised manuscript for better understanding and scientific clarity.
Comment: 1: As explained in the discussion of Figure 2 on XRD, AlN films have biaxial strain that depends on the growth temperature. Although this concept is plausible, the XRD data itself does not seem accurate. If you consider the substrate Si (111) itself, all three XRD plots have a shift in the peak position going towards a lower 2-theta value from a to c. Is there a difference in measurement technique or how the detectors are aligned to the substrate peak? Such a shift could also impact the peak positions of AlN, which is later used to calculate strain. Explain in the paper, how does this impact the shift in the AlN peak that is used to calculate the strain? Suggest repeating the XRD measurements to confirm the peak shifts, if any.
Author Response: We thank the reviewer for their insightful comment. The HRXRD data confirms that the shift in the Silicon peak position is very small; accordingly, all the values were calculated. An explanation is now added in the revised manuscript for better understanding “The sharp peaks at 28.4±0.01° and 58.8±0.01° have been derived from the first and second-order diffractions of Si, identified as the peak corresponding to Si (111) and Si (222), which confirms the presence of Si substrate. Before every HRXRD measurement, the position of the silicon peak was optimized. Therefore the observed shift in the AlN (0002) plane of the grown heterostructure is directly related to the material quality of AlN and not due to detector alignment.”
Comment: 2: If the XRD data is correct, then since there is a growth temperature-dependence of lattice constant of AlN, could deposition at temperatures <770C provide even lower strain? Why is the study limited to 770C-830C?
Author Response: We thank the learned reviewer for careful observation. In the case of the AlN growth at 770oC, the highest incorporation of Al occurs in AlN, leading to a smooth surface. Below 770oC, unreactive Al metal remains on the surface. A comprehensive understanding of the growth of AlN on Si (111) under various growth conditions has been discussed in our earlier report [Aggarwal et al., Springer Nature Applied Science, 2021, 3, 291]. In view of this, all the growth of AlN in this work are performed at T ³770oC.
Comment: 3: Further, it is suggested to include the XRD data for only the AlN buffer layer grown on Si (111) without the GaN layer to fully understand the strain in the AlN itself, and how it is impacted by the growth temperature. Also include SEM images of the AlN buffer layer, to understand how the growth temperature impacts its morphology, and if it has any surface templating effect on the GaN morphology.
Author Response: We welcome the reviewer's suggestion. As explained in comment no 2, the extensive analysis of the growth of AlN on Si has been carried out in our previous report. However, in this work, our focus is to understand the grown GaN and analyze the performance of optoelectronic devices under the influence of an AlN buffer.
Comment: 4: In lines 134-137, it is mentioned that reduced strain leads to "better AlN growth", and later "deteriorated quality...". The use of "better" and "deteriorated" is unclear, since the optoelectronic performance of films with higher strain is still similar, and not significantly worse than nano-obelisk.
Author Response: We really appreciate the diligent reading of the learned reviewer and insightful comments. The better AlN growth was obtained at low buffer layer temperate. The necessary modification has been done in the revised manuscript for better understanding. We have added, “As the growth temperature of the buffer layer increases, a higher strain value was found in the grown AlN.”
Comment: 5: The legends and the plots in Figure 3b-d have GL and RL bands mixed up, making it difficult to follow the explanation. The discussion in lines 181-185 and the Table 1, shows that YL peak is the least for nO while and RL is highest. Does that indicate there are more defects in nO, than nW even if nO has reduced strain? Suggest clarifying these figures and the related discussion.
Author Response: We thank the reviewer for pointing out this. Necessary modifications have been made in the revised manuscript.
Comment: 6: In order to better understand the explanation given through SEM images, it is suggested to include a lower magnification image, as it is critical to see the overall surface morphology across a larger sample area. In lines 201-204, the use of "significantly compact domains and finer structures" must be backed by statistical image analysis comparing grain size. Moreover, in Figure 4a for nO, clear size variation is visible where finer structures are surrounding giant grains, which are even larger than those observed in nW. Looking at the image suggests that overall nP have the most compact grains on average, and nO morphology is the most inconsistent across the imaged area, which is opposite to the explanation given in lines 201-204.
Author Response: We are thankful for this important suggestion. We have added a proper morphological explanation (Interestingly, there is a significant size fluctuation in the structure where nano obelisk finer structures surround by giant grains that are much larger than those seen in nP and nW. The availability of a larger surface area (enormous number of interaction sites) leads to better light-matter interaction) in the revised manuscript. Further, we have provided the low-magnified image of all the samples, and the calculated crystallized size by ImageJ software for nO, nP, and nW have been found to be 80 nm, 119 nm, and 189 nm, respectively. However, the figure is not clear. Therefore we are not added to the main manuscript.
Figure 3: Planar view of FESEM image with low magnification for (a) nO, (b) nP, and (c) nW are shown.
Comment: 7: Kindly explain the significance of the layered structure observed in Figure 4a. Perhaps it is the layered growth features in the nO that result in better PD performance? Other structures do not seem to have this stacked-layer Nano-structuring in the grains.
Author Response: We are thankful to the learned reviewer. The higher performance of the photodetector device depends on multiple factors: the available sites for light-matter interaction, stress, strain, electrodes, etc. In the present case, all films are epitaxially grown using PAMBE. However, in the case of nO, a different growth parameter tuning (the flux of Ga and N reduces graciously. So that we can have the sky tapered obelisks like morphology) has been adopted to achieve a unique structure, which is elaborated in detail in our previous report. [J. Alloys Compd., 2023, 930, 167267]
Comment: 8: Additional analysis would help clarify the observations from the SEM image. First, comparing the FWHM of the GaN and AlN XRD peaks to get the information on crystallize size. Secondly, either an oblique-view SEM or AFM would help support the claim of nO and nP forming "tower-like structures, which leads to larger surface area" in lines 198-199. Finally, EBSD analysis will provide detailed information on the crystalline orientation and strain distribution.
Author Response: We welcome the reviewer suggestion. The low-magnified SEM image shows that the nO structures are very well surrounded by uniform NT. The strain in the film was released due to the formation of this giant structure. Moreover, analyzing the structure using the EBDL measurement technique is an interesting suggestion. Unfortunately, the EBDL is not attached to our system. We will explore the possibility of these measurements in our future studies.
Comment: 9: The comparison of the switching speed of the various morphology is not clear from the plots. So, to make it easier for a reader to observe these differences, it will help if a separate plot is added where the peaks for various morphology are overlaid together. For instance, a normalized Iph plot of a single pulse for a given bias, could enable easier understanding of the peak rise and decay time.
Author Response: We applaud the reviewer's helpful comment. To understand the switching speed of the various structures. We have shown a fitted ON/OFF pulse of transit response observed at 2V for the calculation of rise time and decay time.
Figure 4: A single magnified I−T curve at 2 V bias condition to calculate the rise/decay time for (a) nO, (b) nP, and (c) nW.
Comment: 10: Suggest adding to the methods section, details of the film thickness for both AlN buffer and GaN layers.
Here are some additional suggestions to improve the reading experience of the journal audience:
- This work is similar to the author's previous paper Ref #6 where the effect of AlN buffer layer growth temperature was studied for the properties of AlGaN. It is suggested that a few lines be added in the introduction to explain the findings of Ref #6 and how this manuscript builds on to the prior work.
- The Introduction section must make it clear as to why a larger aspect ratio morphology is preferred over other microstructures.
- A majority of the references, especially in the Introduction section are self-citations and do not capture the whole body of research conducted by the community. Also, an unpublished work cannot be included as a reference, unless it is made public as pre-prints. Relevant references must be added in this manuscript.
- There are some sentences, lines 46-49, 53-55, which are confusing and self-contradictory to the work carried out.
Author Response: We highly appreciate the careful observation of the learned reviewer. We have included all of the modifications indicated by the reviewer, as well as added references relevant to this work. Moreover, in order to eradicate manuscript errors, we carefully revised the manuscript.
Finally, we sincerely thank the reviewer for the careful evaluation and constructive comments to improve the manuscript. Hopefully, the response and the revised manuscript will be acceptable and will accept this work for publication in “Electronic Materials.”
Author Response File: Author Response.docx
Reviewer 3 Report
This paper investigated the influence of AlN layer on material properties. The research is well developed, the results are sound, and beneficial to the optoelectronic applications. However, there are some issues need to be addressed before publication:
1. Background information and motivation of the research should be provided.
2. Line 26. improvised seems like a typo, is it improved?
3. LIne 34. "However, Si has an indirect bandgap; therefore, it requires...." There is a logic jump here. It is hard for non-expertises to understand why a high-pass optical filter because the bandgap value. The author should provide more information here.
4. Line 76. The experimental section. It is highly recommended to have a figure to show the sample preparation process.
5. Line 117. It is recommended to have a figure to show the (0002), (0004) planes, and the crystal structure of the proposed material.
6. Line 121. Please provide definition of nO, nP, and nW.
7. Line 128. It should be pointed out the strain is lattice strain. It is, right?
8. Line 225. (2V to 14V) the right bracket is missing.
Author Response
Response to the Reviewer-3
The manuscript entitled "Stress Relaxed AlN Buffer Oriented GaN-Nano-Obelisks based High-Performance UV-Photodetector" Electronic Materials - Research Article, No. Electronicment-2053832.
We would like to express our gratitude to the reviewer for the thorough review of our manuscript and the valuable comments and suggestions to improve our manuscript. We have addressed all the concerns raised by the reviewer, and a point-by-point response is given below. The manuscript is revised accordingly, and the revisions are highlighted in red.
General Comment: This paper investigated the influence of AlN layer on material properties. The research is well developed, the results are sound, and beneficial to the optoelectronic applications. However, there are some issues need to be addressed before publication:
Author Response: We appreciate the learned reviewer for positive and insightful comments for improving the manuscript. We have addressed all the concerns in the revised manuscript for better understanding and scientific clarity.
Comment: 1: Background information and motivation of the research should be provided.
Author Response: Thank you for your careful reading. We have now added background information and motivation “Recent report indicates that UV radiation has enormous potential in the area of sterilization and disinfection, electronics, biomedicine, air purification, etc. However, high levels of UV radiation may cause a considerable increase in the incidence rate of skin cancer. Because of this, extensive efforts are invested by researchers in the area of UV photodetection technology. A UV photodetection device can convert UV radiation into electrical signals based on the photoelectric effect. Thus, the development of UV photodetection devices has attracted significant attention from researchers worldwide” in the revised manuscript.
Comment: 2: Line 26. improvised seems like a typo, is it improved?
Author Response: We are thankful to the reviewer. This was an oversight by the authors and is now corrected in the revised manuscript.
Comment: 3: LIne 34. "However, Si has an indirect bandgap; therefore, it requires...." There is a logic jump here. It is hard for non-expertises to understand why a high-pass optical filter because the bandgap value. The author should provide more information here.
Author Response: We applaud the reviewer's helpful comment. We have added a proper writeable paragraph in the revised manuscript for better understanding. This is also attached here “Silicon (Si)-based photodetectors are commercially available; however, Si is an indirect bandgap semiconductor (1.1 eV) that requires a high-pass optical filter to stop the high-energy photons”.
Comment: 4: Line 76. The experimental section. It is highly recommended to have a figure to show the sample preparation process.
Author Response: We appreciate your suggestion. We have modified the experimental section of the revised manuscript. Further, a sample preparation process figure has been added here.
Comment: 5: Line 117. It is recommended to have a figure to show the (0002), (0004) planes, and the crystal structure of the proposed material.
Author Response:
Comment: 6: Line 121. Please provide definition of nO, nP, and nW.
Author Response: We highly appreciate the insightful comment of the referee. We have added full form nO, nP, and nW in the revised manuscript.
Comment: 7: Line 128. It should be pointed out the strain is lattice strain. It is, right?
Author Response: We appreciate your suggestion. We have replaced "strain" with "lattice strain" throughout the manuscript.
Comment: 8: Line 225. (2V to 14V) the right bracket is missing.
Author Response: We appreciate your suggestion. We added a bracket in the revised manuscript.
Finally, we sincerely thank the reviewer for the careful evaluation and constructive comments to improve the manuscript. Hopefully, the response and the revised manuscript will be acceptable and will accept this work for publication in “Electronic Materials.”
Round 2
Reviewer 1 Report
The authors addressed my points clearly in the revised manuscript.
Author Response
We would like to express our gratitude and appreciation to the reviewer for the thorough review of our manuscript and the valuable comments and suggestions to improve our manuscript.
Reviewer #1:
Comment: The authors addressed my points clearly in the revised manuscript.
Author Response We would like to thank the learned reviewer for reviewing our manuscript and giving a positive response to the manuscript.
Author Response File: Author Response.docx
Reviewer 2 Report
Authors have made relevant changes to the manuscript based on the reviewer comments. It is suggested that the authors add the following points from their response in the final version of the manuscript to help reader follow the story and read the appropriate literature article:
1. "In the case of the AlN growth at 770oC, the highest incorporation of Al occurs in AlN, leading to a smooth surface. Below 770oC, unreactive Al metal remains on the surface. A comprehensive understanding of the growth of AlN on Si (111) under various growth conditions has been discussed in our earlier report [Aggarwal et al., Springer Nature Applied Science, 2021, 3, 291]. In view of this, all the growth of AlN in this work are performed at T ³770oC." Suggest adding a few lines explaining the same in the Introduction/Methods section, wherever suitable.
2. It is ok to not show the low-magnified SEM image of the samples. However, readers will be interested in learning about the particle size distribution data Suggest adding it in the section explaining the SEM images. "calculated crystallized size by ImageJ software for nO, nP, and nW have been found to be 80 nm, 119 nm, and 189 nm, respectively."
3. Authors mention the following in their response to comment #9. "To understand the switching speed of the various structures. We have shown a fitted ON/OFF pulse of transit response observed at 2V for the calculation of rise time and decay time." Suggest adding this figure in the manuscript.
Author Response
We would like to express our gratitude and appreciation to the reviewe for the thorough review of our manuscript and the valuable comments and suggestions to improve our manuscript. We have addressed all the concerns raised by the reviewer, and a point-by-point response is given below. The manuscript is revised accordingly, and the revisions are highlighted in red.
Reviewer #2:
General Comment: Authors have made relevant changes to the manuscript based on the reviewer comments. It is suggested that the authors add the following points from their response in the final version of the manuscript to help reader follow the story and read the appropriate literature article:
Author Response: We appreciate the learned reviewer for positive and insightful comments for improving the manuscript. We have addressed all the concerns in the revised manuscript for better understanding and scientific clarity.
Comment: 1: In the case of the AlN growth at 770oC, the highest incorporation of Al occurs in AlN, leading to a smooth surface. Below 770oC, unreactive Al metal remains on the surface. A comprehensive understanding of the growth of AlN on Si (111) under various growth conditions has been discussed in our earlier report [Aggarwal et al., Springer Nature Applied Science, 2021, 3, 291]. In view of this, all the growth of AlN in this work are performed at T ³770oC." Suggest adding a few lines explaining the same in the Introduction/Methods section, wherever suitable.
Author Response: We are thankful for the review comment. We are adding the suggested modification in the experimental section of the revised manuscript, which is shown as “Below 760oC, the surface of the inert Al metal still exists. As a result, all AlN growth in this work is carried out at T ≥770 oC”.
Comment: 2: It is ok to not show the low-magnified SEM image of the samples. However, readers will be interested in learning about the particle size distribution data Suggest adding it in the section explaining the SEM images. "calculated crystallized size by ImageJ software for nO, nP, and nW have been found to be 80 nm, 119 nm, and 189 nm, respectively."
Author Response: We highly appreciate the insightful comment of the referee. We have added a full explanation of particle size calculation in the revised manuscript. The explanation is “Further, the calculated crystallized size by ImageJ software for nO, nP, and nW have been found to be 80 nm, 119 nm, and 189 nm, respectively, and the mean size histogram is shown in figure S1, Supporting Information (SI)”.
Comment: 3: Authors mention the following in their response to comment #9. "To understand the switching speed of the various structures. We have shown a fitted ON/OFF pulse of transit response observed at 2V for the calculation of rise time and decay time." Suggest adding this figure in the manuscript.
Author Response: We appreciate the learned reviewer for positive and insightful comments for improving the manuscript. We have added the required figure in the supporting information (figure S2) of the main manuscript. addressed all the concerns in the revised manuscript for better understanding and scientific clarity.
Figure 1: A single magnified I−T curve at 2 V bias condition to calculate the rise/decay time for (a) nO, (b) nP, and (c) nW.
Author Response File: Author Response.docx
