Impact of multi-quantum well growth pressure on GaN-based blue laser diodes

Abstract

This study investigates the influence mechanism of growth pressure during Multiple Quantum Well (MQW) Metalorganic Chemical Vapor Deposition (MOCVD) growth in GaN-based blue laser diodes (LDs). Elevated growth pressure demonstrates an enhancement in LD output performance, seen in both slope efficiency and threshold current, accompanying kinks in P–I curves. To explain these differences in LD performance, we further explore the impact of growth pressure on MQW qualities. Two important influence mechanisms are discussed in detail. concerning indium incorporation during InGaN growth, adatom mobilities are effectively controlled by growth pressure directly during MOCVD growth. We found that higher growth pressure, contributing to rather lower adatom mobilities, facilitates indium incorporation into InGaN MQWs effectively. But excessively high pressure induces severe indium segregation, leading to poor luminescence homogeneity, thus responsible for the observed kinks in P–I curves. Secondly, in regard to crystalline quality of MQWs, impact of interfaces and defects is explored. Lower growth pressure may deteriorate interface quality and trigger more carbon impurity contamination, which are responsible for lower output efficiency that the LDs grown under lower growth pressure exhibit. As a result, we improved the slope efficiency of LD by 30∼40 % successfully by controlling growth pressure during MQW epitaxy.