Study On Ultrafast Carrier Dynamics Of InGaN Based Materials With High In Component

InGaN has been regarded as a new material for fabricating optoelectronic devices because its bandgap can be adjusted from 0.7eV (InN) to GaN (3.4eV) with different ratio of indium (In) component. However it is difficult to grow high-quality InGaN alloy with high In component because of the phase separation induced by large lattice mismatch between InN and GaN. The phase separation can induce quantum-confine effect, localized states and state filling, etc., which can make the optical property and carriers dynamics of InGaN alloy more complicated. There is still lack of enough knowledge on its physical mechanisms. So, it is of great theoretical significance and practical value to research the optical property of InGaN alloy for improving and designing optoelectronic devices.In this dissertation, we investigated the steady state optical spectroscopy and ultrafast carrier dynamics of InGaN based materials with high In component ratio in detail by photoluminescence (PL), time-resolved PL and pump-probe techniques. The main research work and conclusions are listed below.We have studied the stimulated emission and carrier dynamics of InGaN epilayer at room temperature. The stimulated emission was observed under high excitation power. Then we obtained the PL decay curves and transient different reflectivity curves to achieve more information about carrier dynamics under stimulated emission by utilizing time-resolved PL and pump-probe technique. The results clearly reveal a slow multi-step thermalization of hot photo-generated carriers. By comparing PL decay curves and pump-probe results, we found the slow thermalization still exists under stimulated emission. We attributed it to the bottle-neck effect induced by phase separation and In cluster.We have studied the PL property and carrier dynamics of InGaN multiple quantum-wells(QWs) with different periods. We found that the similar slow thermalization still exists in these two samples, and we considered the bottle-neck effect is still the main reason of this phenomenon in multiple quantum well samples.We have studied the PL spectra and carrier dynamics in multiple quantum wells with p-i-n structure. We measured the PL decay curves of p-i-n quantum wells under different excitation power. We found that the PL decay process in p-i-n QWs is obviously slower than those in multi-QWs and film, and strongly depends on the excitation power. We suggested that the screening effect and disscreening effect of electronic field from photo-generated carrier are responsible for these phenomena..