Investigation of trap effects in AlGaN∕GaN field-effect transistors by temperature dependent threshold voltage analysis

TLDR

The study investigates trap effects in AlGaN/GaN and Al₂O₃/AlGaN/GaN HFETs via temperature‑dependent threshold voltage analysis. The authors analyze threshold voltage shifts in both HFET and MOSHFET devices up to 450 °C to assess trap behavior. The threshold voltage of both HFET and MOSHFET devices decreases with temperature up to 450 °C, revealing donor traps with a shift of −1.6 mV/°C for HFETs and −8.5 mV/°C for MOSHFETs, a thermally activated level of ~0.2 eV attributed to nitrogen vacancies, and a trap density about twice as high in MOSHFETs likely due to the ~600 °C gate‑insulator deposition.

Abstract

We report on a temperature dependent threshold voltage analysis of the AlGaN∕GaN heterostructure field-effect transistors (HFETs) and Al2O3∕AlGaN∕GaN metal-oxide-semiconductor HFETs (MOSHFETs) in order to investigate the trap effects in these devices. The threshold voltage of both types of devices decreases with increased ambient temperature up to 450°C. This indicates on donor traps to be present. The temperature induced threshold voltage shift is −1.6 and −8.5mV∕°C for the HFETs and MOSHFETs, respectively. A thermally activated energy level of ∼0.2eV is evaluated and attributed to the nitrogen vacancy in the AlGaN near surface. The trap density for the MOSHFETs is about two times higher than that for the HFETs. This might be due to the high-temperature treatment (∼600°C) of the MOSHFET structure during the gate insulator deposition.