Buffer-Induced Time-Dependent OFF-State Leakage in AlGaN/GaN High Electron Mobility Transistors on Silicon

摘要

Time-dependent OFF-state leakage behavior of AlGaN/GaN MISHEMTs on silicon substrate is investigated and a novel degradation mechanism is proposed in this paper. Under constant high voltage OFF-state stress, drain leakage current gradually increases with stress time and the behavior is gate bias and temperature-dependent. Consecutive OFF-state breakdown measurement with drain injection technique indicates that the negative shift of threshold voltage ( Vth ) is responsible for the increase of drain leakage current during stress measurement. It is proposed that the negative shift of Vth is mainly induced by the ionization of uncompensated donor like deep levels near the channel, which are most likely to be located in the 300-nm-thick unintentionally doped GaN layer above the carbon doped buffer layer.