Spectroscopy of Non-Radiative Recombination Centers in Semiconductors for Light Emitting Devices

1. 摘要：通过观察间隙下激发（BGE）光与间隙上激发（AGE）光叠加导致的带对带光致发光（PL）强度变化，可以定量研究本体和多量子阱（MQW）半导体中的非辐射复合（NRR）中心。将AGE密度降低到单光子计数水平，可以提高发现NRR中心的灵敏度。通过调节AGE和bge的能量，可以清楚地了解NRR中心的能量分布及其在MQW结构中的空间分布。GaAs/AlGaAs MQW结果：(1)在未掺杂和掺硅样品中检测到不同水平的GaAs/AlGaAs MQW，反映了它们的结构和生长条件。(2)综合考虑AGE和BGE的能量依赖性，确定了捕集器的空间和能量分布。(3)与均匀掺杂相反，调制掺杂井层中NRR中心的缺失首次被明确。(4)考虑AGE和BGE密度依赖性，自洽地确定捕集器参数。在GaN基半导体中：(1)在InGaN/GaN MQW中，在GaN层中发现了NRR中心，BGE能量区域在1.6 ~ 2.4 eV之间。(2)在本体GaN样品中获得了相同的能量分布，表明与MQW的结果一致。(3)检测到GaN/AlGaN MQW中的NRR中心，可用于分析详细的重组动力学。

1. General : By observing the intensity change of band-to-band photoluminescence (PL) due to the superposition of a below-gap excitation (BGE) light on an above-gap excitation (AGE) light, a quantitative study on nonradiative recombination (NRR) centers in bulk and multiple quantum well (MQW) semiconductors became possible. Lowering the AGE density down to the single-photon-counting level improved the sensitivity of finding NRR centers. The energy distribution of the NRR centers and their spatial distribution in MQW structures became clear by tuning the energy of AGE and BGE.2. Results in GaAs/AlGaAs MQW :(1) Various levels were detected in undoped and Si-doped samples, reflecting their structures and growth conditions.(2) Spatial and energy distribution of traps was determined by considering AGE and BGE energy dependence.(3) Contrary to uniform-doping, absence of NRR centers in modulation-doped well layers became clear for the first time.(4) Trap parameters were determined self-consistently by considering the AGE and BGE density dependence.3. Results in GaN-based Semiconductors :(1) In InGaN/GaN MQW, NRR centers were found in GaN layers with the BGE energy region between 1.6 and 2.4 eV.(2) The same energy distribution was obtained in bulk GaN sample, indicating the consistency with the result of MQW.(3) NRR centers in GaN/AlGaN MQW were detected, which can be utilized for analyzing detailed recombination dynamics.