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

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 〈 11 2 ¯ 0 〉 / { 1 1 ¯ 00 } and 〈 11 2 ¯ 0 〉 / { 1 1 ¯ 01 } slip systems. This result illustrates the importance of threading dislocation mobility in controlling the reliability of AlGaN/GaN-on-Si HEMTs.