Chapter 6 - Persistent photoconductivity in III-nitrides

Abstract

This chapter reviews the persistent photoconductivity (PPC) in III-nitrides and provides an overview of such an effect in these materials. It also discusses the PPC characteristics including its buildup and decay behaviors, evidence of DX-like centers, the nature of defects, implications on PPC mechanisms, effects of PPC on III-nitride devices including field effect transistors (FETs) and photodetectors. The properties of PPC and associated deep level centers in III-nitrides have built on the studies on AlGaAs alloys. The deep level centers and the associated PPC effect have been observed in a wide variety of III-nitride materials and structures. Their presence indicates possible charge trapping or charge freeze out effects in III-nitride devices, which could cause instabilities in such devices and hence have significant influences on the device performance. Current devices in the III-nitrides take advantages of heterostructures and quantum wells. As the nitride materials quality improves, the nature of deep level center as well as their characteristics can be identified. Due to their wide band gaps, effects of deep level centers on the III-nitride materials and devices are expected to be more pronounced than in narrower band gap materials.