Direct observation of 0.57 eV trap-related RF output power reduction in AlGaN/GaN high electron mobility transistors

This paper reports direct evidence for trap-related RF output power loss in GaN high electron mobility transistors (HEMTs) grown by metal organic chemical vapor deposition (MOCVD) through increased concentration of a specific electron trap at EC−0.57 eV that is located in the drain access region, as a function of accelerated life testing (ALT). The trap is detected by constant drain current deep level transient spectroscopy (CID-DLTS) and the CID-DLTS thermal emission time constant precisely matches the measured drain lag. Both drain lag and CID-DLTS measurements show this state to already exist in pre-stressed devices, which coupled with its strong increase in concentration as a function of stress in the absence of significant increases in concentrations of other detected traps, imply its role in causing degradation, in particular knee walkout. This study reveals EC−0.57 eV trap concentration tracks degradation induced by ALT for MOCVD-grown HEMTs supplied by several commercial and university sources. The results suggest this defect has a common source and may be a key degradation pathway in AlGaN/GaN HEMTs and/or an indicator to predict device lifetime.

► EC−0.57 eV deep level observed in all MOCVD-grown GaN HEMTs.
► EC−0.57 eV level increases ∼5× with high temperature RF stressing.
► Pulsed I–V exhibit increased knee walkout due to EC−0.57 eV level.
► EC−0.57 eV deep level associated with and possible source of HEMT degradation.
► Deeper levels show no consistent relation with HEMT degradation.