蓝光激光器结构中InGaN/GaN多量子阱界面效应的精细光致发光光谱研究

金属有机化学气相沉积(MOCVD)方法制备InGaN/GaN多量子阱结构时,在GaN势垒层生长的N2载气中引入适量H2,能够有效改善阱/垒界面质量从而提升发光效率.本工作利用光致发光(PL)光谱技术,对蓝光激光器结构中的InGaN/GaN多量子阱的发光性能进行了精细的光谱学测量与表征,研究了通H2生长对量子阱界面的调控...

Fine Photoluminescence Spectroscopic Characterization of Interfacial Effects on Emission Properties of InGaN/GaN Multiple Quantum Wells in a Blue-Light Laser Diode Structure

In growing InGaN/GaN multiple quantum wells (MQWs) with the technique of metal-organic chemical vapor deposition (MOCVD), the introduction of an appropriate amount of H₂ into the N₂ carrier gas for the growth of the GaN barrier layers can effectively improve the crystalline quality of the well/barrier interface and therefore enhance the luminescence efficiency of the quantum wells. In this work, we carried out detailed photoluminescence (PL) spectroscopic measurements on the luminescence properties of InGaN/GaN MQWs in the device structure for blue-light laser diodes, and the effects of H₂ in the carrier gas for GaN barrier growth on the MQWs, including the improved interface quality, the enhanced luminescence and the underlying mechanisms, have been investigated. The PL spectra of the InGaN/GaN MQWs acquired at room temperature reveal that the introduction of 2.5% H₂ in the N₂ carrier gas leads to increased emission efficiency by 75%, blue-shifted peak energy by 17 meV, and narrowed full width at half maximum (FWHM) by 10 meV. With the PL spectra measured at varied excitation powers, the quantum-confined Stark effect (QCSE) and band-filling effect on the emission performance of the MQWs have been distinguished, and the QCSE effect is found to dominantly determine the emission energy and width, which can be effectively reduced by the introduction of H₂. Upon the complete screening of the QCSE effect, the peak energy of the MQWs emission is located at 2.75 eV. The dependence of the PL spectra on temperature indicates that the introduced H₂ in the carrier gas can also reduce the carrier localization effect and narrow the energy fluctuation of the well potential, which leads to the narrowed PL spectral width in the samples grown with the mixture of H₂/N₂ carrier gas. The variation of the PL intensity with respect to temperature reveals that the physical nature of the nonradiative recombination centers at the interface is not influenced by the introduction of H₂, but the amount of these centers is greatly reduced, which accounts for the improved emission efficiency. The results of time-resolved PL measurements exhibit that the introduced H₂ in the carrier gas has no impact on the nonradiative recombination lifetime, but causes a shorter radiative recombination lifetime, which further confirms the influences of H₂ introduction on both QCSE screening and nonradiative recombination centers. The in-depth analyses of the PL results have revealed that the introduction of H₂ in the N₂ carrier gas for GaN barrier growth can significantly improve the crystalline quality of InGaN/GaN MQWs and therefore enhance the light emission performance. This work has demonstrated PL spectroscopy as a powerful technique in characterizing the optical properties of semiconductor quantum structures, and the spectral findings could provide helpful insight into the growth of InGaN/GaN MQWs.