Spatially-resolved spectroscopic measurements of <i>Ec</i> − 0.57 eV traps in AlGaN/GaN high electron mobility transistors

Abstract

Simultaneous temperature-dependent measurements of resistance transients (RTs) and spatially resolved surface potential transients were made after bias switching on AlGaN/GaN high electron mobility transistors (HEMTs). We find an Ec − 0.57 eV trap, previously correlated with HEMT degradation, located in the GaN buffer and not in the AlGaN barrier or at the AlGaN surface. The amplitude of the Ec − 0.57 eV trap in RTs depends strongly on the Fe-concentration in the GaN buffer. Filling of this trap occurs only under bias conditions where electric fields penetrate into the GaN buffer.