Department of Physics, ‡Department of Electrical Engineering, §Department of Chemical Engineering and Materials Science, and ⊥Center for Energy Nanoscience, University of Southern California , Los Angeles, California 90089, United States.
ACS Nano. 2015 Feb 24;9(2):1336-40. doi: 10.1021/nn505227q. Epub 2015 Jan 21.
Unlike nanowires, GaAs nanosheets exhibit no twin defects, stacking faults, or dislocations even when grown on lattice mismatched substrates. As such, they are excellent candidates for optoelectronic applications, including LEDs and solar cells. We report substantial enhancements in the photoluminescence efficiency and the lifetime of passivated GaAs nanosheets produced using the selected area growth (SAG) method with metal organic chemical vapor deposition (MOCVD). Measurements are performed on individual GaAs nanosheets with and without an AlGaAs passivation layer. Both steady-state photoluminescence and time-resolved photoluminescence spectroscopy are performed to study the optoelectronic performance of these nanostructures. Our results show that AlGaAs passivation of GaAs nanosheets leads to a 30- to 40-fold enhancement in the photoluminescence intensity. The photoluminescence lifetime increases from less than 30 to 300 ps with passivation, indicating an order of magnitude improvement in the minority carrier lifetime. We attribute these enhancements to the reduction of nonradiative recombination due to the compensation of surface states after passivation. The surface recombination velocity decreases from an initial value of 2.5 × 10(5) to 2.7 × 10(4) cm/s with passivation.
与纳米线不同，即使在晶格失配的衬底上生长，砷化镓纳米片也没有孪晶缺陷、堆垛层错或位错。因此，它们是光电应用的优秀候选材料，包括 LED 和太阳能电池。我们报告了使用金属有机化学气相沉积（MOCVD）的选择区域生长（SAG）方法制备的钝化砷化镓纳米片的光致发光效率和寿命有了显著提高。在有和没有 AlGaAs 钝化层的情况下对单个砷化镓纳米片进行了测量。通过稳态光致发光和时间分辨光致发光光谱来研究这些纳米结构的光电性能。我们的结果表明，AlGaAs 对砷化镓纳米片的钝化导致光致发光强度提高了 30 到 40 倍。光致发光寿命从不到 30 增加到 300ps，表明少数载流子寿命提高了一个数量级。我们将这些增强归因于钝化后表面态补偿导致非辐射复合减少。表面复合速率从初始值 2.5×10^5 降低到 2.7×10^4 cm/s。
