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Article
Peer-Review Record

Effect of Annealing Time of GaN Buffer Layer on Curvature and Wavelength Uniformity of Epitaxial Wafer

Condens. Matter 2025, 10(2), 28; https://doi.org/10.3390/condmat10020028
by Huanyou Wang 1,2,*, Guangqi Xie 2,* and Yingying Zhan 1
Reviewer 1: Anonymous
Reviewer 2:
Reviewer 3: Anonymous
Condens. Matter 2025, 10(2), 28; https://doi.org/10.3390/condmat10020028
Submission received: 31 March 2025 / Revised: 27 April 2025 / Accepted: 28 April 2025 / Published: 1 May 2025

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this paper, the authors present an analysis of the GaN buffer layer curvature versus annealing time. I suggest minor revisions on this paper. Please find below my comments:

Page. 2 line 71: It is not clear to me if furnace A, B, C are three actual different furnaces, or if the samples A, B, C were created in the same furnace/reactor with different annealing times.

Author Response

Response to Reviewer 1 Comments

1. Summary

 

 

Thank you very much for taking the time to review our manuscript. We sincerely thank you for your careful work, and thank you very much for your affirmation of our work. According to your valuable comments and suggestions, we have mainly made the following explanations and revisions.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Yes

 

Is the research design appropriate?

Yes

 

Are the methods adequately described?

Yes

 

Are the results clearly presented?

Yes

 

Are the conclusions supported by the results?

Yes

 

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: Page. 2 line 71: It is not clear to me if furnace A, B, C are three actual different furnaces, or if the samples A, B, C were created in the same furnace/reactor with different annealing times.

Response 1:

The samples A, B and C were successively created in the same reactor at different annealing times. Because this experimental equipment can only grow 24 pieces at a time, we have explained it in line 56 on the second page.

4. Response to Comments on the Quality of English Language

The English is fine and does not require any improvement.

Response:  

Reviewer 2 Report

Comments and Suggestions for Authors

The background section of the article is too general and does not provide a detailed picture of the field and related technological advances.

I don't understand why only three variables for a single parameter were selected, it would be too minimal of an effort. Or may I ask why only 40 seconds, 50 seconds and 55 seconds were chosen?

Necessary simulations or experiments for theoretical calculations should be added!

The quality of Figure 5 is too low.

The conclusion is too short without detailed analysis of the results, which is also related to the small number of experiments in this paper.

More references need to be cited for the reader's convenience.

English statements and word spelling need to be further improved.

Author Response

Response to Reviewer 3 Comments

1. Summary

 

 

Thank you very much for taking the time to review our manuscript. You suggested some important opinion in our original version. We sincerely thank you for your careful work. According to your valuable comments and suggestions, we have mainly made the following explanations and revisions.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Must be improved

Have revised

Is the research design appropriate?

Can be improved

Have explained in the point-to-point response

Are the methods adequately described?

Can be improved

Have explained in the point-to-point response

Are the results clearly presented?

Can be improved

Have revised

Are the conclusions supported by the results?

Can be improved

Have revised

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: The background section of the article is too general and does not provide a detailed picture of the field and related technological advances.

Response 1: We have added detailed picture of the field and related technological advances. 

The added content can be found in the revised draft.

Comments 2: I don't understand why only three variables for a single parameter were selected, it would be too minimal of an effort. Or may I ask why only 40 seconds, 50 seconds and 55 seconds were chosen?

Response 2: To ensure the accuracy of the experimental data, only the annealing time of the buffer layer was changed this time, and no other parameters were changed. As for why we chose 40 seconds, 50 seconds and 55 seconds, this is determined based on our experience over the past few years. The optimal annealing time may vary for different equipment and different growth parameters. For example, for MOCVD with different numbers of pieces and wafer diameter, the annealing time of the buffer layer may vary.

Comments 3: Necessary simulations or experiments for theoretical calculations should be added!

Response 3: Dear reviewer, as far as we know and have consulted many literature, there is currently no research on the effect of GaN buffer layer annealing time on epitaxial layer warping. To ensure the accuracy of the experimental data, only the annealing time of the buffer layer was changed this time, and no other parameters were changed. The curvature values of the u-GaN end and the third quantum well are collected. Due to the influence of many factors on the photoemission spectrum wavelength of InGaN-based LEDs, such as growth temperature, pressure, flow rate, time, and thickness, especially the structure of quantum wells. The quantum well structure has a decisive impact on the emission wavelength, such as the thickness of the well and barrier, the number of periods, and the content of In and Ga in the quantum well, among which the content of In and Ga is the key factor. The content of In and Ga in quantum wells is closely related to the growth temperature of quantum wells, so we focused on introducing the growth temperature of each functional layer in the experimental section. Although our research has achieved some results, the results are not yet ideal enough, and we will continue to study further.

Comments 4: The quality of Figure 5 is too low.

Response 4: We have replaced Figure 5. The sampling resolution is 23 × 23. Since this image contains 72 PL-Mapping, the clarity appears not high. Fig. 5 shows the PL-mapping chart of dominant wavelengths of all samples in furnace A, B, and C. The blue color indicates that the actual wavelength is shorter than the target wavelength, and the red color indicates that the actual wavelength is longer than the target wavelength. The statistical results of this figure can be found in table 1.

Comments 5: The conclusion is too short without detailed analysis of the results, which is also related to the small number of experiments in this paper.

Response 5: We have made revisions to the conclusion section. The specific revisions can be found in the revised draft.

Comments 6: More references need to be cited for the reader's convenience.

Response 6: We have added the references. The added references can be found in the revised draft.

4. Response to Comments on the Quality of English Language

Comment: English statements and word spelling need to be further improved.

Response: We have used MDPI Author Services to edit the English of our manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

The Authors have reported an interesting study regarding GaN buffer layer and wavelength uniformity. Given the present interest in GaN and LEDs in general, their work represents a timely contribution to these interesting research fields. Although this work warrants publication in some form, the Authors must address the following issues before I can recommend the publication of this paper in Condensed Matter.

1. It is a strange not to set the step of the annealing time to be 10 s. In other words, the annealing time could have been 40, 50 and 60 sec. Why it is not the case? The Authors ought to elaborate.

2. The top two layers are p-doped GaN and AlGaN as shown in Fig. 1. Please mention how these two layers were prepared.

3. I feel that the Authors ought to mention some interesting work on GaN grown on different substrates. For example, GaN epitaxial film can be grown on a lattice-matched (100) β-LiGaO2 substrate (D. R. Hang, M. M. C. Chou, L. Chang, Y. Dikme, and M. Heuken, J. Crystal Growth 311, 452 (2009) and M. M. C. Chou, C. L. Chen, D. R. Hang,  and W. T. Yang, Thin Solid Films 519, 5066 (2011).

4. Finally, could the Authors comment on the possiblity of preparing their samples on a Si substrate since they will be Si CMOS compatible, please?

Author Response

Response to Reviewer 4 Comments

1. Summary

 

 

Thank you very much for taking the time to review our manuscript. We sincerely thank you for your careful work, and thank you very much for your affirmation of our work. According to your valuable comments and suggestions, we have mainly made the following explanations and revisions.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Yes

 

Is the research design appropriate?

Yes

 

Are the methods adequately described?

Yes

 

Are the results clearly presented?

Yes

 

Are the conclusions supported by the results?

Yes

 

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1:  It is a strange not to set the step of the annealing time to be 10 s. In other words, the annealing time could have been 40, 50 and 60 sec. Why it is not the case? The Authors ought to elaborate.

Response 1: To ensure the accuracy of the experimental data, only the annealing time of the buffer layer was changed this time, and no other parameters were changed. As for why we chose 40 seconds, 50 seconds and 55 seconds, this is determined based on our experience over the past few years. The optimal annealing time may vary for different equipment and different growth parameters. For example, for MOCVD with different numbers of pieces and wafer diameter, the annealing time of the buffer layer may vary.

Comments 2: The top two layers are p-doped GaN and AlGaN as shown in Fig. 1. Please mention how these two layers were prepared.

Response 2: Thank you for your careful work. We missed some parameters. We have added parameters to the revised draft.

Comments 3: I feel that the Authors ought to mention some interesting work on GaN grown on different substrates. For example, GaN epitaxial film can be grown on a lattice-matched (100) β-LiGaO2 substrate (D. R. Hang, M. M. C. Chou, L. Chang, Y. Dikme, and M. Heuken, J. Crystal Growth 311, 452 (2009) and M. M. C. Chou, C. L. Chen, D. R. Hang,  and W. T. Yang, Thin Solid Films 519, 5066 (2011).

Response 3: Although we did not discuss the influence of different substrates separately, it can be seen in the references that there are many different substrates, such as pre-strained sapphire substrates, pre-warped substrate, patterned silicon substrate et al. We downloaded the article you mentioned and conducted research on it. We found that these articles were quite different from our research content and would not be added to our articles.

Comments 4: Finally, could the Authors comment on the possiblity of preparing their samples on a Si substrate since they will be Si CMOS compatible, please?

Response 4: We know that light-emitting diodes are generally grown on silicon, sapphire and silicon carbide substrates. We are relatively familiar with the growth of light-emitting diodes, but we are not familiar with the growth of CMOS on silicon substrates and have not conducted any research. Therefore, it is not convenient for us to comment.

4. Response to Comments on the Quality of English Language

The English is fine and does not require any improvement.

Response:  

 

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The author has revised and improved it as required.

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