Effect of AlGaN/GaN Strained-Layer Superlattices Underlayer to InGaN-based Multi-Quantum Wells Grown on Si(111) Substrate by MOCVD

摘要

We report superior improvement of optical and structural properties by insertion of Al_(0.06)Ga_(0.94)N/GaN strained-layer superlattices (SLS) underlayer to InGaN-based multi-quantum wells (MQW) structure grown on Si(111) substrate with combination of AlN nucleation layer and AlN/GaN intermediate layer. In photoluminescence (PL) surface mapping, insertion of Al_(0.06)Ga_(0.94)N/GaN SLS underlayer improves MQW emission wavelength uniformity and exhibits a narrower emission full-width at half maximum (FWHM) than that of sample with conventional GaN underlayer. Integrated intensity of temperature-dependent photoluminescence (PL) spectra indicates that higher internal quantum efficiency ((eta)_(iqe)) of 32.9percent is obtained in sample with Al_(0.06)Ga_(0.94)N/GaN SLS underlayer than that of 26.4percent in GaN underlayer. Scanning transmission electron microscopy (STEM) analysis shows that the Al_(0.06)Ga_(0.94)N/GaN SLS layer abruptly bends threading dislocation lines, thus reduces penetration of threading dislocations to the MQW. It therefore improves (eta)_(iqe) of the MQW.