Rectifying Characteristics of Thermally Treated Mo/SiC Schottky Contact
Round 1
Reviewer 1 Report
The authors present an interesting work on the effects of annealing temperature and time on the Schottky barrier height and ideality factor of Mo/SiC Schottky diodes. They show two different methods of extracting the Schottky barrier height and show the two methods have similar results. However, a number of amendments are required before the manuscript should be accepted for publication.
1. Throughout the manuscript, the authors have not used subscripts or superscripts, so some quoted values are unrealistic, such as the saturated electron velocity of SiC being “2x107 cm/s” on page 1, line 31. These need to be amended.
2. On page 2, line 53 the authors refer to a Schottky metal. This is not a well-known material, so could the authors explain the difference between a Schottky metal and a normal metal.
3. The symbols of the Schottky-Mott relationship on page 2, line 55 are not clearly defined. It would aid the reader if the authors could label these symbols as part of their summary of this relationship in line 53.
4. The facing targets sputtering system shown in Figure 1 on page 2 is very interesting and not commonly seen. It would help the understanding of the readers if additional labels were added to explain the location of the substrate and the sputtering target.
5. In the current form, the structure of the back-side Ohmic contact is unclear from line 88, page 3. The space between Ni/Ti/NiV and /Ag makes it confusing for the reader. A diagram of the device would aid in the understanding of the reader.
6. The Mo and Al sputtering targets on page 3, lines 90-92 should be described as such as the current phrasing makes it sound like they were placed onto the SiC wafer for the contacts.
7. Table 1 on page 3 only seems to have parameters for Ti deposition, or were these parameters common to all three metals listed in this table? Also, if the deposition was carried out in-situ, how were the Ni, NiV and Ag deposited for the back-side electrode as these metals are not included in the table?
8. Figure 2 is very unclear and the change in axis scale on the voltage at 0 V makes it difficult for the reader to understand the changes under different annealing conditions.
9. The forward voltage is typically determined from the linear scale of the current density vs voltage plot and not the semi-logarithmic one. The authors should include the linear scale plot to allow the reader to fully appreciate the change in forward voltage and to show the trend with respect to annealing temperature and time, as described in page 3, line 108.
10. Throughout the second paragraph on page 3, the authors refer to an I-V curve when figure 2 shows a J-V curve. The authors should correct their terminology to aid the reader.
11. There seems to be very little change in the reverse current for all 5 samples, though both the 10 minute and 30 minute anneal at 400ºC show a slight increase in reverse current of approximately the same magnitude when compared to the as-deposited device. Therefore the claim in line 110, page 3 seems to be unsubstantiated based on the data presented in Fig. 2.
12. In Fig. 3a, there seems to be a data point added at J=0A/cm2 that appears to skew the results as the trend of the data except this point tends to be linear, meaning the linear fit for the Cheung & Cheung method to determine the ideality factor is not clear. This could also explain the non-ideal behavior of the diodes in the low-voltage region of the curve. This data point also does not appear to be present in Fig. 3b, which based on the methodology, should show a very similar trend to Fig. 3a. It would also aid the reader if the current density scales in Fig. 3a and 3b were plotted with the same limits.
13. Fig. 4 is rather unclear and it is difficult for the reader to understand the trends at voltages below 0.75 V. The authors could use the same color scheme as in Fig. 2 and 3 to aid comprehension and add a second panel to this figure showing the low voltage region below 1 V.
14. The determination of Schottky barriers is dependent on temperature, yet there is no mention of what temperature the measurements were carried out at. It would aid the reader to be provided with this vital piece of information to be able to relate it to the charge injection mechanism and the energy of the system.
15. In the Norde method, the authors seemed to arbitrarily choose a constant γ of 2 and 3 (page 4, line 134). Why were these values in particular chosen?
16. Table 2 has not been included in the manuscript.
17. To avoid confusion to the reader, the authors should change their terminology which tends to relate to transistors, so that “threshold voltage” is referred to as “forward voltage” and “leakage current” is “reverse current”.
18. After annealing there appears to be a clear change in peak shape of the XRD patterns shown in Fig. 6, particularly for the peaks near 35º and 75º when compared to the as deposited sample, even though the intensity appears to be unchanged. What are the possible reasons for the change in shape?
19. On page 6, line 196 the units of the Schottky barrier heights are missing.
Author Response
Dear reviewer
Please find the revised manuscript (Coatings-524699) through the uploaded file entitled “Rectifying Characteristics of Thermally Treated Mo/SiC Schottky Contact”. The manuscript has been revised based on the reviewer’s comments. The modified and added parts in the text are in red characters.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This work is a good complement to the field. While all the conclusions are sound, some minor changes are necessary for a better expression.
Figure 5, the authors provide a description in the figure caption, however, it is not very straightforward. A good figure should be clear and self-explained. The authors shall try to improve this figure by introducing colors or legend.
Line 88, 5×1015/cm3. I think this might be caused from the font or style change, the authors might need to pay attention to this when submitting the final manuscript.
Author Response
Dear Reviewer
Please find the revised manuscript (Coatings-524699) through the uploaded file entitled “Rectifying Characteristics of Thermally Treated Mo/SiC Schottky Contact”. The manuscript has been revised based on the reviewer’s comments. The modified and added parts in the text are in red characters.
Author Response File: Author Response.docx
Reviewer 3 Report
The article is well written and scientifically sound. However, the reviewer would like to address some specific questions. It is correct that SiC is the most promising material for next-generation power semiconductors but also GaN is widely studied for this application and therefore should be mentioned in the introduction. In order to introduce the work function, a band diagram would be more suitable and clarifies a lot. Some typos are present in lines 88,89 and 147. Also, to verify if Al0.5Fe0.5 are for the sample holder, please show the peaks (XRD measurement) for the bare sample holder. If possible, provide temperature dependent photoluminescence (PL) or TEM measurements as XRD provides global structure information TEM could provide better insights on the structure changes responsible to the observed behavior. Also EBIC-SEM could provide a better understanding of the transport mechanism.
Author Response
Dear Reviewer
Please find the revised manuscript (Coatings-524699) through the uploaded file entitled “Rectifying Characteristics of Thermally Treated Mo/SiC Schottky Contact”. The manuscript has been revised based on the reviewer’s comments. The modified and added parts in the text are in red characters.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors have addressed the concerns highlighted in the previous round of review, and it now presents a clearer impression of the work carried out in this manuscript on Schottky barriers at the junction between Mo and SiC.
Reviewer 3 Report
It is a pity the time is not enough for the additional PL, TEM or EBIC-SEM experiments. Despite, the reviewer thinks it could bring more light to the observed behavior it is true that the main finding is correctly addressed and therefore the reviewer thinks the article should be accepted in present form.
