UV Emission Mechanisms in Quaternary AlInGaN Epilayers and Multiple Quantum Wells
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UV Emission Mechanisms in Quaternary AlInGaN Epilayers and Multiple Quantum Wells Mee-Yi Ryu, C. Q. Chen, E. Kuokstis, J. W. Yang, G. Simin, M. Asif Khan, G. G. Sim,1 and P. W. Yu1 University of South Carolina, Department of Electrical Engineering, Columbia, SC 29208, U.S.A. 1 Dept. of Information and Communications, Kwangju Institute of Science and Technology, Kwangju, 500-712, Republic of Korea ABSTRACT We present the results on investigation and analysis of photoluminescence (PL) dynamics of quaternary AlInGaN epilayers and AlInGaN/AlInGaN multiple quantum wells (MQWs) grown by a novel pulsed metalorganic chemical vapor deposition (PMOCVD). The emission peaks in both AlInGaN epilayers and MQWs show a blueshift with increasing excitation power density. The PL emission of quaternary samples is attributed to recombination of carriers/excitons localized at band-tail states. The PL decay time increases with decreasing emission photon energy, which is a characteristic of localized carrier/exciton recombination due to alloy disorder. The obtained properties of AlInGaN materials grown by a PMOCVD are similar to those of InGaN. This indicates that the AlInGaN system is promising for ultraviolet applications such as the InGaN system for blue light emitting diode and laser diode applications. INTRODUCTION Ultraviolet (UV) light emitting diodes (LEDs) with emission in the range of 300 – 350 nm are ideal for pumping the fluorescent film of full color display devices. The most promising materials for active layers of such UV emitters are either ternary AlxGa1-xN [1,2] or quaternary AlxInyGa1-x-yN [3-7] due to the desired wide direct band gap range. We have reported on deep UV LEDs with emission from 305 to 340 nm using AlInGaN multiple quantum wells (MQWs) in the active region [3-5]. In our work the AlInGaN MQW layers for the active region were deposited using a pulsed atomic layer epitaxy (PALE) approach. Recently, we have also demonstrated a new pulsed metalorganic chemical vapor deposition (PMOCVC) procedure [6,7]. The two procedures differed mainly in the group V (NH3) precursor supply. In PMOCVD the group III metalorganic (MO) precursors were pulsed and the NH3 supply was kept on all the time, whereas in PALE both the MO and the NH3 were pulsed and alternatively supplied in the growth chamber. High quality quaternary AlInGaN layers would be grown by either of the two procedures. However, the spontaneous photoluminescence (PL) intensity of the PMOCVD layer was in general higher than that of the PALE deposited material. In this study we report on the PL emission and dynamics studies of quaternary AlInGaN epilayers and AlInGaN/AlInGaN MQWs grown by a PMOCVD procedure. EXPERIMENTAL DETAILS The quaternary samples used in this study were grown on (0001)-oriented sapphire substrate by a PMOCVD. Prior to the deposition of the quaternary AlInGaN epilayers or MQWs, about a 1-µm-thick intrinsic GaN epilayer was deposited on a sapphire substrate with a 25-nm-thick AlN K1.7.1 Downloaded from https://www.cambridge.org/core. University
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