PNNL

Abstract

GaN template layer strain effects on the growth of InGaN/GaN light emitting diodes (LED) devices were investigated. Seven-period InGaN/GaN multiple quantum well structures (MQW) were deposited on 5µm and 15µm GaN template layers. It was found that the electroluminescence (EL) emission of the 15µm device was red-shifted by approximately 132meV. Triple-axis X-Ray Diffraction (TAXRD) and Cross-Sectional Transmission Electron Microscopy (XTEM) show that the 15µm template layer device was virtually unstrained while the 5µm layer experienced tensile strain. Dynamic Secondary Ion Mass Spectrometry (SIMS) depth profiles show that the 15µm template layer device had an average indium concentration of 11% higher than that of the 5µm template layer device even though the MQW structures were deposited during the same growth run. It was also found that the 15µm layer device had a higher average growth rate than the 5µm template layer device. This difference in indium concentration and growth rate was due to changes in thermodynamic limitations caused by strain differences in the template layers.