An analytical model on the gate control capability in p-GaN Gate AlGaN/GaN high-electron-mobility transistors considering buffer acceptor traps

An analytical model considering the buffer acceptor traps is presented in this paper to study the gate control capability in p-GaN gate AlGaN/GaN high-electron-mobility transistors (HEMTs). Through applying Gauss' law from the buffer layer to the two-dimensional-electron-gas (2DEG) channel in the GaN channel layer, the contributions of buffer acceptor trap concentration (N-A) and energy level (E-T) are obtained for calculating the gate voltage (V-G) dependent 2DEG density (n(S)) and threshold voltage (V-TH) performance. It is suggested that the deep E-T acceptor traps in the buffer layer are of great importance to the gate control capability. Plenty of the deep E-T acceptor traps could be ionized at the top region of the buffer layer. These ionized acceptor traps are negatively charged and electrostatically influence the 2DEG density, which is the role of deep E-T on gate control. Then, the n(S)-V-G and V-TH characteristics of the devices could be significantly modulated by the N-A. Furthermore, the influence of the shallow E-T acceptor traps is not strong and could be ignored in the prediction of the n(S)-V-G and V-TH distributions. This is due to the fact that few shallow E-T acceptor traps are ionized in the buffer layer. The analytical results are well supported by the calibrated TCAD simulation, revealing the impact mechanism of buffer acceptor traps on the device gate control capability and serving as more accurate guidance for designing the n(S)-V-G and V-TH in p-GaN gate AlGaN/GaN HEMTs.