Recombination Process in InGaN/GaN MQW LED on Silicon with δ-Si Doped n-GaN Layer

The emission efficiency of InGaN/GaN multiple quantum well(MQW) light emitting diode(LED) reduces if it is grown on single crystalline silicon substrates because of the enhanced strain between interfaces. A possible strategy to solve this problem is introducing periodic Si δ-doped GaN instead of Si uniformly doped GaN as the n-GaN layer. In this work, steady-state(SS) photoluminescence spectra(PL) and time-resolved(TR) PL spectra for LED sample with either Si uniformly doped GaN or periodic Si δ-doped GaN working as n-type GaN layer were tested for comparison. Relative emission efficiencies and recombination rates for each sample were extracted, then systematically analyzed. The results turned out that: the main PL peak redshifted from 531 nm to 579 nm after introducing periodic Si δ-doped n-GaN layer; the average activation energy related to nonradiative recombination increased from (18±3) meV to (38±10) meV, as well as the decreasing of nonradiative recombination rate became slower with increasing temperature, and the nonradiative recombination rate at room temperature became smaller; at the same time, the average radiative recombination rate decreased with increasing temperature in major temperature range, which indicated that exciton localization dominated the radiative recombination processes. The average depth of localized state for excitons increased and the average radiative recombination rate at low temperature decreased. To sum up, because of the releasing of strain in MQW, the defect density that related to nonradiative recombination can be reduced, and the device performance can be improved if using periodic Si δ-doped n-GaN layer to replace Si uniformly doped GaN working as n-type GaN layer in InGaN/GaN MQW LED on silicon substrate. © 2018, Science Press. All right reserved.