硅衬底生长的InGaN/GaN多层量子阱中δ型硅掺杂n-GaN层对载流子复合过程的调节作用

为了解决在单晶硅衬底上生长的InGaN/GaN多层量子阱发光二极管器件发光效率显著降低的问题，使用周期性δ型Si掺杂的GaN取代Si均匀掺杂的GaN作为n型层释放多层界面间的张应力。采用稳态荧光谱及时间分辨荧光谱测量，提取并分析了使用该方案前后的多层量子阱中辐射/非辐射复合速率随温度（10~300 K）的变化规律。实验结果表明引入δ-Si掺杂的n-GaN层后，非辐射复合平均激活能由（18±3）meV升高到（38±10）meV，对应非辐射复合速率随温度升高而上升的趋势变缓，室温下非辐射复合速率下降，体系中与阱宽涨落有关的浅能级复合中心浓度减小，PL峰位由531 nm左右红移至579 nm左右，样品PL效率随温度的衰减受到抑制。使用周期性δ型Si掺杂的GaN取代Si均匀掺杂的GaN作为生长在Si衬底上的InGaN/GaN多层量子阱LED器件n型层，由于应力释放，降低了多层量子阱与n-GaN界面、InGaN/GaN界面的缺陷密度，使得器件性能得到了改善。

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.