Electrical characterization of GaN Schottky barrier diode at cryogenic temperatures

Abstract

In this report, electrical characteristics of the Ni/GaN Schottky barrier diode grown on sapphire have been investigated in the range of 20 K–300 K, using current–voltage, capacitance–voltage, and deep level transient spectroscopy (DLTS). A unified forward current model, namely a modified thermionic emission diffusion model, has been developed to explain the forward characteristics, especially in the regime with a large ideality factor. Three leakage current mechanisms and their applicability boundaries have been identified for various bias conditions and temperature ranges: Frenkel–Poole emission for temperatures above 110 K; variable range hopping (VRH) for 20 K–110 K, but with a reverse bias less than 20 V; high-field VRH, in a similar form of Fowler–Nordheim tunneling, for cryogenic temperatures below 110 K, and relatively large bias (>25 V). Four trap levels with their energy separations from the conduction band edge of 0.100 ± 0.030 eV, 0.300 eV, 0.311 eV, and 0.362 eV have been tagged together with their capture cross sections and trap concentrations. The significantly reduced DLTS signal at 100 K suggested that traps practically became inactive at cryogenic temperatures, thus greatly suppressing the trap-assisted carrier hopping effects.