Thermionic emission dominated carrier dynamics in InGaN/GaN multiple quantum-wells

Summary form only given. We report on our study of the carrier dynamics in InGaN/GaN MQWs by using femtosecond pump-probe transmission measurements. Our study indicates the existence of a strong barrier field, which is in balance with the strong piezoelectric field within the QWs. After photocarriers have been excited by optical pulses, the thermionically emitted electrons and holes were found to be driven by the barrier field toward different sides of the MQWs, which caused the electron/hole wavefunction separation. The space charge field induced by the separated electrons and holes will screen out part of the barrier field and increase the total electric field in the QWs. Due to the existing barrier field, a weak dependence of the thermionic emission time on the barrier width was observed. Our study suggests that the separated electron/hole wavefunctions might lead to decreased wavefunction overlaps and cause the increased carrier lifetime.