Transient current spectroscopy of lattice matched InAlN/AlN/GaN HFETs for identification of traps resulting in gate lag

Abstract

GaN-based heterojunction field effect transistors (HFETs) are strong contenders to replace vacuum tubebased devices in the high power, and high frequency arena. However, the piezoelectric stain, exploited to generate high density two-dimensional electron gases (2DEGs) in AlGaN/GaN devices is not necessarily desirable nor might it bode well in terms of device reliability. By using lattice-matched InAlN as the barrier, even higher densities of 2DEG and now respectable DC and RF performance can be achieved while at the same time avoiding the strain and subsequent reliability issues in the devices. However, little work has been done in identification of trapping mechanisms in the InAlN-based devices. The trapping is at the heart of the reduced RF performance of all the GaN-based devices, limiting the maximum attainable RF power. In this work, transient current spectroscopy, which observes the dynamics of the drain current during gate lag measurements, is utilized to ascertain information about the trapping levels, cross sections, and spatial locations of traps in the InAlN-based devices. Preliminary measurements indicate that one of the traps identified in this work (at 0.12eV) is similar to one measured by deep level transient spectroscopy (DLTS) in similar structures. Investigations of this type are imperative for the further development and implementation of this highly promising material system.