Hot electron induced non-saturation current behavior at high electric field in InAlN/GaN heterostructures with ultrathin barrier

Lei Guo,Xinqiang Wang,Ning Tang,Jianpeng Cheng,Jie Zhang,Xuelin Yang,Weikun Ge,Anqi Hu,Zhihong Feng,Yuanjie Lv,Bo Shen

doi:10.1038/srep37415

Abstract

The high-field transport characteristics of nearly lattice-matched InAlN/GaN heterostructures with different barrier thickness were investigated. It is found that the current in the InAlN/GaN heterostructures with ultrathin barrier shows unsaturated behaviors (or secondary rising) at high voltage, which is different from that of AlGaN/GaN heterostructures. This phenomenon is more obvious if the barrier thickness is thinner and the channel width is narrower. The experimental results demonstrate that it is the increasing carrier density excited from the more defect states by the hot electrons with larger electron saturation velocity that results in the unsaturated current behaviors in InAlN/GaN heterostructures. Our results pave a way for further optimizing InAlN barrier design and improving the reliability of InAlN/GaN HEMTs.

Highlights

GaN-based high electron mobility transistors (HEMTs) are promising devices for generation high frequency and high power applications[1,2]
Several questions related to the device reliability at high electric field are still open for InAlN/GaN HEMTs
There are large density of defects which may correlate to the problem of more serious degradation of the InAlN/GaN HEMTs6–8

Summary

Methods

The In0.18Al0.82N/GaN and Al0.24Ga0.76N/GaN heterostructures used in this work were grown on c-plane sapphire substrate by metal-organic chemical vapor deposition (MOCVD). The channel dimensions (L ×W) are 10 μm × 15 μm, and the mesa was etched down to the substrate. The sample’s mesa was fabricated with an H-shaped geometry (Fig. 1) which may (i) make the electric field in the channel homogenous, (ii) minimize the effects of contact resistance, and (iii) control the carrier injection from the Ohmic contacts[25]. The contact resistance was 0.9 Ω · mm estimated at low electric fields by transmission line model (TLM). The channel at the middle was passivated with a 100 nm Si3N4 passivation layer. High-field current-voltage (I-V) characteristics were obtained by nanosecond pulsed technique on H-shape sample mounted in a 50 Ω matched circuit. The voltage pulse length was fixed at 80 ns with a repetition rate of 1 Hz in order to minimize the self-heating effect

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