Local trap spectroscopy on cross-sectioned AlGaN/GaN devices with in situ biasing

Abstract

Scanning probe deep-level transient spectroscopy (SP-DLTS) is applied to cross-sectioned, fully processed, commercially sourced AlGaN/GaN Schottky barrier diodes (SBDs) and high electron mobility transistors (HEMTs) biased in situ. The SBD and HEMT structures had been specially designed to allow two- and three-terminal biasing after cross-sectioning. The cross-sectioning procedure exposes electrically active regions throughout the length and depth of the devices while also preserving electrical functionality. Spatially resolved SP-DLTS surface potential transients (SPTs) measured on the appropriately cross-sectioned faces of the devices reveal the presence of two traps in the GaN buffer layer which are shown to be consistent with traps detected in macroscopic deep-level transient spectroscopy measurements performed on an intact AlGaN/GaN SBD made at the same time as the HEMT device. This indicates that, for an appropriate cross-sectioning process, the cross-sectioned surface does not screen or mask defects in the bulk GaN from the probe tip. SP-DLTS maps collected over the cross-sectioned faces in active device regions also reveal the spatial variation in trapping-induced SPTs. These measurements demonstrate an avenue for exploring the energies, concentrations, and spatial distributions of traps located throughout GaN-based devices with potential applications to other material and device systems.