Increasing N content in GaNAsP nanowires suppresses the impact of polytypism on luminescence

Cathodoluminescence (CL) and micro-photoluminescence spectroscopies are employed to investigate effects of structural defects on carrier recombination in GaNAsP nanowires (NWs) grown by molecular beam epitaxy on Si substrates. In the NWs with a low N content of 0.08%, these defects are found to promote non-radiative (NR) recombination, which causes spatial variation of the CL peak position and its intensity. Unexpectedly, these detrimental effects can be suppressed even by a small increase in the nitrogen composition from 0.08% to 0.12%. This is attributed to more efficient trapping of excited carriers/excitons to the localized states promoted by N-induced localization and also the presence of other NR channels. At room temperature, the structural defects no longer dominate in carrier recombination even in the NWs with the lower nitrogen content, likely due to increasing importance of other recombination channels. Our work underlines the need in eliminating important thermally activated NR defects, other than the structural defects, for future optoelectronic applications of these NWs.

本研究采用阴极荧光（Cathodoluminescence, CL）与显微光致发光（micro-photoluminescence）光谱技术，探究了分子束外延生长于硅衬底上的GaNAsP纳米线（nanowires, NWs）中结构缺陷对载流子复合过程的影响。在氮含量仅为0.08%的低氮纳米线中，这类结构缺陷会促进非辐射（non-radiative, NR）复合，进而导致CL峰位与峰强出现空间分布不均的现象。出乎意料的是，仅将氮组分从0.08%小幅提升至0.12%，即可抑制上述有害效应。该现象可归因于氮诱导的局域化效应可更高效地将激发载流子/激子束缚于局域态，以及体系中存在的其他非辐射复合通道。在室温条件下，即便在低氮含量的纳米线中，结构缺陷也不再主导载流子复合过程，这可能源于其他复合通道的重要性显著提升。本研究强调，若要实现这类纳米线在未来光电子器件中的应用，需针对性消除除结构缺陷之外的关键热激活非辐射缺陷。