Optical and structural properties of dual wavelength InGaN/GaN multiple quantum well light emitting diodes

摘要

The optical and structural properties of Charge Asymmetric Resonance Tunneling (CART) structure InGaN/GaN multi-quantum wells (MQWs) grown on sapphire by metalorganic chemical vapor deposition (MOCVD) have been investigated by optical measurements of temperature-dependent photoluminescence (PL), photoluminescence excitation (PLE) and time-resolved photoluminescence (TRPL), and high-resolution transmission electron microscopy (HRTEM). Two typical samples are studied, both consisting of six periods of CART InGaN wells with 3.3 nm thickness and with 8.5 nm thickness of GaN barrier, respectively, and two periods of InGaN wells with 2 nm thickness of 7 nm GaN barrier with different well growth-temperature of 797°C and 782°C, respectively. According to the PL measurement results, large values of activation energy are obtained. The decrease of well growth-temperature results higher In composition and also in the increase of composition fluctuation in the InGaN MQW region, showing the stronger carrier localization effect and large values of activation energy and Stokes' shift are obtained. The lifetime at the low-energy side of the InGaN peaks is longer for higher indium composition.