Browsing by Author "Sharma, Chandan"

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Effects of gamma-Ray Irradiation on AlGaN/GaN Heterostructures and High Electron Mobility Transistor Devices
(1970-01-01)
Sharma, Chandan
;
Singh, Rajendra
;
Chao, Der-Sheng
;
Wu, Tian-Li
;
國際半導體學院
This study examined the effects of three cumulative c-ray irradiation doses on AlGaN/GaN epilayer material and on high electron mobility transistor (HEMT) devices. After a cumulative gamma-ray dose of 16 kGy, the Hall mobility increased from 1800 cm(2)/V s to 2100 cm(2)/V s, as determined through Hall measurement. Atomic force microscopy indicated an improvement in surface roughness but no change in the surface potential (theta(s)). The HEMT device exhibited improvement in the drain current, with a subtle decreasing tendency in the leakage current. At high doses of gamma-ray irradiation, the trends in the material and device parameters saturated. Moreover, the metal-semiconductor interface degraded, as confirmed through scanning electron microscopy image analysis.
Investigation of the degradations in power GaN-on-Si MIS-HEMTs subjected to cumulative gamma-ray irradiation
(2019-09-01)
Sharma, Chandan
;
Modolo, Nicola
;
Chen, Hsi-Han
;
Tseng, Yang-Yan
;
Tang, Shun-Wei
In this work, GaN-on-Si power Metal-Insulator-Semiconductor High Electron Mobility Transistors(MIS-HEMTs) are irradiated through different regimes of cumulative gamma-ray irradiation, namely 1, 2, 3, 4, and 5 kGy for the first sample; 1, 3, and 5 kGy for the second sample; 1, 5, and 10 kGy for the third sample; and 1, 10, and 20 kGy for the fourth sample. After each irradiation dose, drain current (ID), threshold voltage (I-g), and gate leakage current (Is) are electrically characterized in all the samples. An improvement in I-D with a shift in V-Th is observed in all the samples, which saturates after a higher irradiation dose. X-ray photoelectron spectroscopy (XPS) analysis confirms creation of nitrogen vacancies that act as donor and improves the I-D. No significant change in I-g is observed except for an increase in noise in gate leakage current. Scanning electron microscopy (SEM) shows the Al-based metallization pad degrades due to formation of small cavities. Finally, energy dispersive X-ray (EDX) analysis confirms the formation of Al native oxides due to gamma-ray irradiation.
Understanding gamma-Ray Induced Instability in AlGaN/GaN HEMTs Using a Physics-Based Compact Model
(2020-03-01)
Sharma, Chandan
;
Modolo, Nicola
;
Wu, Tian-Li
;
Meneghini, Matteo
;
Meneghesso, Gaudenzio
In this article, we demonstrate that a physics-based compactmodel can facilitate to analyze the reliability using an example of gamma-ray induced instability in AlGaN/GaN HEMTs. First, the typical AlGaN/GaN HEMTs are subjected to the cumulative gamma-ray irradiation, exhibiting the drain current (I-D) increase. In order to further elucidation, the root cause, the compact model is implemented and calibrated with the pristine case. Then, I-D-V-G and I-D-V-D characteristics subjected to the gamma-ray irradiation are fitted with the compact model. The extracted mu and R-c are consistent with the results obtained by the Hall measurement and circular transmission line measurement (C-TLM). By comparing the fitted curves with considering: 1) fitted mu (R-c is fixed as the pristine case) and 2) fitted R-c (mu is fixed as the pristine case), the shift of mu is identified as the root cause leading to the I-D increase because of the better fitting results. Therefore, with the assistance of the physics-based compact model, the shift of the parameter can be further analyzed to understand the origin of the instability.