Study On The Optical Properties Of InGaN/GaN Multiple Quantum Wells

The III-V nitride-semiconductor as represented by GaN is the third generation of semiconductor materials developing in recent decade. These semiconductor materials have excellent optical and electrical performance. By controlling their respective component, their band gap can continuously change from0.7eV of InN to3.4eV of GaN nutil6.2eV of A1N, which cover the entire visible light district and expand to the scope of the UV.In recent years, GaN-based optoelectronic materials and devices have been rapidly developed, but there are still some problems to be solved. In this paper, we studied the optical properties of InGaN/GaN multiple quantum wells (MQWs) by use of the method of photoluminescence (PL). The main research work and results are as follows:1. Excitation power dependence of the PL spectra was studied in InGaN/GaN MQWs at a temperature of6K. The excitation power dependences of the PL peak energy and linewidth indicate that the emission process of the MQWs is dominated first by the screening effect of the quantum confined Stark effect (QCSE) and then by the band-filling effect.2. The dependence of the PL spectra on various temperatures was also reported. We observed an S-shaped (decrease-increase-decrease) temperature dependence of the peak energy for InGaN-related PL with increasing temperature. This anomalous emission behavior is attributed to a change in the carrier dynamics with increasing temperature due to inhomogeneity and carrier localization in the InGaN/GaN MQWs. 3. Two InGaN/GaN MQWs samples with different substrates were grown for the comparison of localization states. By analyzing different temperature dependences of the PL spectra of the two samples, we deduced that the sample with a slower growth rate has a relatively uniform distribution of localization states.4. In the PL spectra, there is a broad deep level emission at lower energy under the conditions of low excitation powers and medium temperatures. This can be attributed to the emission from deep localization states which contain higher indium contents.