Enhancing the blue GaN laser diodes by modifying the first barrier structure and adjusting the growth conditions of quantum wells

Abstract

The structure of the first barrier (FB) of quantum wells was modified from the single-layer GaN to the GaN-InGaN-GaN composite structure. Experiments have shown that the composite first barrier can improve the crystal quality of the quantum wells, which increase the luminous power and reduce the stress accumulation before the InGaN quantum well. Furthermore, the composite first barrier can reduce the polarized electric fields and suppress the impact of quantum confinement Stark effect (QCSE) on the luminescence properties of the quantum wells. The growth conditions of the InGaN/GaN quantum wells were studied. Both the growth rate and the ammonia flow are related to the incorporation of In in InGaN quantum wells and the formation of In clusters. These two parameters have optimal values when the other one is fixed. After optimizing the growth rate and the ammonia flow, the internal quantum efficiency of the quantum wells was finally improved from 24.14 % to a commercial level of 77.2 %.