Characterization of different trap states in AlGaN/GaN MIS-HEMTs under high reverse gate stress

Abstract

In this work, we have studied the degradation of AlGaN/GaN MIS-HEMTs under reverse gate stress. It found that the origin of the threshold voltage shift (ΔVTH) is not derived from the barrier layer defect, but is closely related to the gate dielectric layer. In order to investigate it, two types of trap states (traps A and B) with different properties in AlGaN/GaN MIS-HEMTs gate dielectrics were proposed and studied by the constant stress-recovery experiment and thermal detrapping technique. Trap A is related to the precursor defect with transient characteristics. Trap B with permanent characteristics is newly generated during the stress, which dominates the permanent degradation and induces the breakdown. Furthermore, according to the measurement results of ΔVTH and injected-electron density (Ninj), the capture cross sections of traps A and B have been extracted, which are 5.52 × 10−21cm2 and 1.38 × 10−22cm2, respectively.