Formation mechanism of trench defects in green InGaN/GaN multiple quantum wells

Abstract

Trench defects, resulting in low emission efficiency in green and longer spectrum ranges, are widely observed in III-nitride alloy multiple quantum wells (MQWs), particularly in those with high indium content. There is a lack of understanding of the atomic formation mechanism of trench defects; however, it is crucial to the efficiency of devices. Here, we provided a thermodynamic analysis through first-principles calculations based on the density functional theory combined with experimental confirmation to reveal the atomic formation mechanism of trench defects in the InGaN MQWs system. The In-rich region is easy to form and induces basal plane stacking faults (BSFs) at the interface between the InGaN quantum well and the GaN quantum barrier (QB). The boundary between BSF and non-BSF regions exhibits a much slower growth rate due to the formation of homoelementary bonds, resulting in a V-shaped groove shape. Based on high-angle annular dark field scanning transmission electron microscopy, we observe the trench defects originating from the thick GaN QB layer due to the formation of closed-loop V-shaped grooves and the BSF. Besides, the cathodoluminescence measurements show that the InGaN QW within the defect has excess indium and poor crystal quality.