Study of Stimulated Emission in InGaN/GaN Multi-Quantum Wells in the Temperature Range of 175 k to 575 k
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ABSTRACT We present the results of an experimental study on stimulated emission (SE) in optically pumped InGaN/GaN multi-quantum well (MQW) structures in the temperature range of 175 K to 575 K. Samples used in this work consisted of 12 QWs and the GaN barriers were intentionally doped with different Si concentrations. The effect of doping on the SE thresholds of the MQWs were investigated. We observed that the SE spectra were comprised of many narrow peaks of less than I A full width at half maximum (FWHM). No broadening of the FWHMs of the peaks occurred as the temperature was raised from 175 to 575 K. The SE threshold was measured as a function of temperature and compared with that of a thin GaN film. Low SE thresholds were attributed to high quantum efficiency of the MQWs, possibly associated with large carrier localization. A characteristic temperature of 162 K was derived from the temperature dependence of the SE threshold. The integrated emission intensity versus pumping density was examined for different temperatures. This study shows that InGaN/GaN MQWs are suitable for the development of laser diodes that can operate well above room temperature. INTRODUCTION Wide band-gap III-V nitrides have attracted much attention due to their potential applications for solar-blind detectors [1], high-power microwave devices [2], and light emitting devices [3]. GaN-based structures have been shown to be chemically stable and able to withstand high temperatures [4,5]. Recently commercialized bright blue light emitting diodes and demonstrated current-injection cw laser diodes are all based on InGaN/GaN heterostructures. The low temperature sensitivity of the lasing threshold in ridge-geometry InGaN multi-quantum well (MQW) structure near room temperature (RT) in comparison to structures based on other III-V and I1-VI materials [6-8] prompts further research to explore possibilities of high temperature applications for III-V nitride MQWs. In this work, we report the results of an experimental study on SE in optically pumped InGaN/GaN MQW samples in the temperature range of 175-575 K. The SE threshold was studied as a function of temperature and compared to the SE threshold of a GaN thin film. Characteristic temperatures were derived from the temperature sensitivity of the SE threshold to be 166 K and 162 K for a GaN film and an InGaN/GaN MQW sample, respectively. The effects of Si doping on the SE thresholds of InGaN/GaN MQWs were evaluated experimentally. Also, we examined the dependence of the integrated emission intensity on pumping density for different temperatures. Finally, we discuss the possibilities for development of InGaN/GaN MQW-based optoelectronic devices capable of high temperature operation.
199 Mat. Res. Soc. Symp. Proc. Vol. 512 ©1998 Materials Research Society
EXPERIMENT The InGaN/GaN MQW samples used in this work were grown on a 1.8 pm thick GaN base layer by metalorganic chemical vapor deposition (MOCVD) using the precursors trimethylgallium (TMGa), trimethylindium (TMIn), trimethylaluminum (TMAI),
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