The Influence of Traps on the Self-Heating Effect and THz Response of GaN HEMTs

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The title effectively incorporates critical keywords such as "traps," "self-heating," "THz response," and "GaN HEMT," which are also reflected in the abstract. However, the abstract lacks a clear problem statement that motivates the study. Current research on traps in GaN HEMTs often focuses on their role in current collapse or reliability issues, but the interplay between traps, self-heating, and THz response remains underexplored. Explicitly stating this research gap in the abstract would strengthen its alignment with the title and clarify the study’s novelty.

 

1. The paper mentions that traps introduce new energy levels that prolong carrier lifetime. Could you specify these traps' exact energy levels (in eV) relative to the conduction and valence bands, and justify their assumed positions in the simulation?
2. You note that high trap concentrations (>1e16 cm³) exacerbate current collapse. Is this solely due to mobility degradation from lattice heating, or do the traps directly contribute to enhanced phonon scattering? Please clarify the interplay between traps and self-heating.
3. The local maxima in Udc at 4e15 cm⁻³ and 7e15 cm⁻³ are attributed to plasma wave damping and temperature-gradient-induced fields. Could you provide a quantitative model or analytical expression linking these trap concentrations to the observed peaks?
4. You mention that simulations struggle to converge for abrupt boundary conditions or high trap densities. What specific numerical adjustments (such as mesh refinement or solver settings) were made to ensure accuracy, particularly for the 5e17 cm³ case?
5. Equation (2) describes trap capture/emission rates, but how does the carrier lifetime (τ) quantitatively scale with trap concentration? Is there a saturation point beyond which additional traps no longer increase τ?
6. The paper assumes non-resonant detection but does not explicitly calculate τ for the simulated traps. What values of τ were derived, and how do they compare to the 0.1-THz excitation frequency?
7. You suggest that this field opposes the THz response. How was its magnitude estimated in the simulation, and does it correlate with the local temperature profiles in the channel?
8. Table 2 lists default mobility values for silicon, but the device uses AlGaN/GaN. Were material-specific parameters used? If not, how might this affect the results?
9. The Idmin/Idmax ratio is used to quantify self-heating. Why not use thermal resistance (Rth) or peak channel temperature, which are more direct indicators?
10. You recommend a trap concentration of 4e15 cm³ for balancing conductivity and THz response. Is this value universally optimal, or does it depend on device geometry (e.g., gate length, AlGaN thickness)?
11. Several references (e.g., [9]–[13]) discuss self-heating but do not explicitly address the effects of traps. Are there more targeted studies that link traps to self-heating in GaN HEMTs, which could strengthen the literature review?
12. The introduction's phrase broad room for it to develop is unclear. Could you rephrase this for better readability, such as "significant potential for development"?
13. Please ensure the following papers are cited where relevant:

   - (https://doi.org/10.1088/2053-1591/abff0a) (for trap characterization in GaN). 

   - (https://doi.org/10.1016/j.spmi.2021.107045) (for THz response modeling). 

   - (https://doi.org/10.1007/s10854-022-09549-z) (for self-heating mitigation techniques). 

 

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript titled "The Influence of Traps in Self-heating Effect and THz Response of GaN HEMT" provides an in-depth analysis and investigation of the degradation characteristics of traps in GaN-based HEMT devices on the self-heating effect and their weakening impact on the THz response. It innovatively proposes a method to mitigate the unavoidable performance degradation caused by traps by intentionally introducing traps. The explanation regarding the improvement of channel conduction characteristics using the relationship between trap emission and capture rates is highly convincing and logically sound. Overall, the manuscript presents a clear and well-structured argument, offering strong guidance for trap engineering in devices. This manuscript can be accepted after minor revisions, with the following suggestions:

 

1. For the sake of rigor, the legend in Figure 10 should include a concentration unit, and the legend in Figure 7 should include a voltage unit.
2. The mesh setup in the simulation is a critical aspect; a figure showing the mesh distribution near the channel can be added to the manuscript.

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

In this study, the authors systematically investigate the influence of trap concentration on self-heating effects and terahertz (THz) response characteristics in GaN HEMT devices , resulting in that traps significantly enhance channel current by providing new energy levels that prolong carrier lifetime. Furthermore, they provide optimization guidelines for trap engineering in GaN HEMT devices. However, there are some details that deserve in-depth study. Therefore, this manuscript can be accepted for publication after minor revisions.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The quality of the Figures is very poor; no one can see what you mentioned. All the Figures in the papers must be revised; you should use a standard font size and TIMES NEW Roman characters. YOU SHOULD consider this A MAJOR REVISION. The abbreviations need to be defined when they first appear in the paper, but keep in mind that the Abstract and conclusion can't be considered in the overall paper.

Comments on the Quality of English Language

Still needs grammatical revision

Author Response

Thank you for your feedback. We've adjusted the image format according to your suggestions, and refined the English wording.