Characterization and simulation of gallium vacancies in the InGaN layer

Low-In-content InGaN bulk layers are widely used in GaN-based LDs, LEDs, and vertical p-n diodes. However, studies on point defects in InGaN bulk layers are still relatively rare. Due to their thin thickness when grown on GaN template layers, methods for characterizing point defects in unintentionally doped InGaN bulk layers are lacking. To address this, we proposed fabricating photodetectors using u-InGaN bulk layers and analyzing their photoresponse characteristics to study point defects. Our findings revealed a significant persistent photoconductivity (PPC) effect in u-InGaN bulk layers grown at low temperatures with a high V/III ratio. By integrating temperature-dependent photoluminescence (TDPL), secondary ion mass spectrometry (SIMS), and first-principles calculations, we attributed this phenomenon to gallium vacancy defects (V_Ga). Adjusting the growth temperature and V/III ratio effectively mitigates the impact of V_Ga defects.