Threading dislocation movement in AlGaN/GaN-on-Si high electron mobility transistors under high temperature reverse bias stressing

C L Gan,W A Sasangka,G J Syaranamual,C V Thompson,R I Made

doi:10.1063/1.4962544

Abstract

Dislocations are known to be associated with both physical and electrical degradation mechanisms of AlGaN/GaN-on-Si high electron mobility transistors (HEMTs). We have observed threading dislocation movement toward the gate-edges in AlGaN/GaN-on-Si HEMT under high reverse bias stressing. Stressed devices have higher threading dislocation densities (i.e. ∼5 × 109/cm2) at the gate-edges, as compared to unstressed devices (i.e. ∼2.5 × 109/cm2). Dislocation movement correlates well with high tensile stress (∼1.6 GPa) at the gate-edges, as seen from inverse piezoelectric calculations and x-ray synchrotron diffraction residual stress measurements. Based on Peierls stress calculation, we believe that threading dislocations move via glide in 〈112¯0〉/{11¯00} and 〈112¯0〉/{11¯01} slip systems. This result illustrates the importance of threading dislocation mobility in controlling the reliability of AlGaN/GaN-on-Si HEMTs.

Highlights

There is strong interest in monolithic integration of AlGaN/GaN high electron mobility transistors (HEMTs) with Si-complementary metal-oxide semiconductor (CMOS)[1] circuits
Under high temperature reverse bias stressing, AlGaN/GaN HEMTs degrade over time through a decrease of the drain saturation current[3] and/or an increase gate leakage current.[4,5,6]
It can be seen that the dislocation pits are uniformly distributed across the device at ∼2.5 × 109/cm[2]. This is comparable with the initial threading dislocation density (TDD) of the GaN epitaxial film as purchased.[16]

Summary

INTRODUCTION

There is strong interest in monolithic integration of AlGaN/GaN high electron mobility transistors (HEMTs) with Si-complementary metal-oxide semiconductor (CMOS)[1] circuits. It is widely accepted that this physical and performance degradation can be explained by electrochemical oxidation of AlGaN/GaN at the gate-edges.[10] Recently, we have shown that pit formation is associated with threading dislocations and suggested that threading dislocations catalyze pit formation and thereby decrease device life-times.[12] In this paper, we report experimental evidence of dislocation movement in AlGaN/GaN HEMTs under high temperature reverse bias stressing. This has the effect of increasing the dislocation and pit density at the gate edges, and further contributes to the degradation of device performance

EXPERIMENTAL DETAILS

RESULTS AND DISCUSSION

CONCLUSIONS