Growth optimisation of GaInN/GaN MQW RCLED structures. Device performances and reliability

Abstract

In this paper, we report on the growth optimisation and characterisation of GaInN/GaN Multiquantum Well (MQW) RCLED structures emitting at 500nm. The device structures, which include GaInN/GaN MQW and GaAlN/GaN Bragg mirrors, have been grown by MOCVD, and their physical properties were optimised using High Resolution X−Ray Diffraction (HR−Xray) and room temperature photoluminescence mapping measurements. The correlation of some physical properties of the epitaxial structures with the device characteristics, such as the optical performances or the reliability, has been investigated. The growth of GaInN/GaN MQW heterostructures is not straightforward, and the well/barrier interface optimisation is a critical step of the RCLED MOCVD process due to the large difference in the growth parameters of GaN and GaAlN. A drastic improvement of the luminescence efficiency of the GaInN/GaN MQW heterostructures has been obtained for MQW/Barriers grown at low temperature (700°C/980°C) with thickness around 8A/90A. This breakthrough in the optical properties can be explained by the fact that the thin quantum wells grown at low temperature may favour the quantum dot formation and a good lateral carrier confinement due to an inherent built in piezo−electric field across the well. The 300K photoluminescence efficiency obtained at 499nm was found to be 100 times higher as compared to the previous MQW heterostructures emitting at the same wavelength, with a different design (30A/90A) and grown at higher temperatures (820°C/1150°C). Figure 1 shows a room temperature photoluminescence mapping of the peak wavelength ( = 499nm ) related to