Revised CV characterization technique for interface state evaluation in SiN/n-GaN MIS capacitors: Effects of extraction time, temperature and UV illumination

Abstract

Interface defects at dielectrics/III-nitride interfaces can lead to significant threshold voltage shifts in GaN-based MIS or MOS FETs and dynamic RDS,on in HEMTs. Currently, the interface state density, Dit, is often quantified by deviations in the measured capacitance of a stressed curve in relation to an ideal reference curve. However, the influence of measurement parameters, such as sweeping rate and stress conditions, on extracted Dit values remains poorly understood. This study presents an improved method for characterizing interface state densities in dielectric/n-GaN MIS capacitors, were we derive quasi-static CV curves from transient measure-stress-measure measurements at room temperature and elevated temperatures and apply the photo-assisted HF CV technique. Using the Terman method, we extract time-dependent changes in interface charges and show that the extracted Dit distribution depends on the exact choice of extraction time, temperature and UV intensity. We demonstrate that the derived Dit can vary by an order of magnitude and peak positions can shift by 0.4 eV depending on the voltage and measurement conditions, which should be chosen according to the capture/emission dynamics of defects.