Back Bias Effects in AlGaN/GaN HFETs

Abstract

HFETs were grown by MOVPE consisting of 28 nm AlGaN on 1 μm GaN (all undoped) on conducting, n-type, 4H-SiC. The conducting nature of the SiC allowed a substrate bias to be applied to the device giving the opportunity to change the 2DEG concentration by changing the GaN depletion region width, and so obtain information about the electrically active centres in the semiinsulating GaN. It was shown that the GaN material was p-type with a net (deep level) acceptor density of ∼1.5 x 10 17 cm -3 , which dropped with increasing depth below the surface.