Optical performance of Zn, Si doped GaAs nanowires

Objective Nanowires (NWs), being one-dimensional (1D) semiconductor materials, hold considerable value due to their distinctive properties in various nanoscale optoelectronic devices. Silicon based optoelectronic technology has high compatibility with microelectronic processes, and the research and development of heteroepitaxial III-V group compounds on silicon are rapidly advancing, enabling the fabrication of silicon photonic chips. Considering the application of doped nanowires in p-n junctions and optoelectronic integrated devices, as well as the rapid development of the micro-optoelectronic industry, the research on Si based doped GaAs nanowires is of great significance. Under the influence of the tide to combine the III-V group compounds with silicon, Zn, Si doped GaAs NWs have been successfully grown on Si/SiO₂ substrates using MOCVD technology. In order to explore the Zn, Si doping effects on the optical performance of GaAs NWs, variable temperature and power density photoluminescence (PL) measurement have been conducted on each sample. This manuscript will provide technical reserves and theoretical support for the further research and development of GaAs nanowires.

Methods Zn, Si doped and undoped GaAs NWs have been grown via MOCVD technology under some growth conditions. The only distinguishment between three grown samples are the addition of two different dopants, which are SiH₄ and DEZn. The growth morphology of three samples were detected through SEM measurement (Fig.1) in order to verify the successful growth of nanowires. The optical performance of Zn, Si doped nanowires was contrasted through low temperature PL spectrum (Fig.2). The luminescence origins of each sample were distinguished through 15 K variable power density PL tests (Fig.3). Subsequently, variable temperature PL tests were performed on each sample to verify the degree of fitting between peak position altering pattern with temperature and theoretical values (Fig.4). In the end, necessary TEM measurement was conducted on Zn doped sample to explore its structure characteristics.

Results and Discussions The growth morphology of three samples were detected through SEM measurement. The nanowires were grown via VLS growth mechanism on silicon substrates and the growth direction is random and chaotic (Fig.1). The optical performance of Zn, Si doped nanowires was contrasted through low temperature PL spectrum (Fig.2). The luminescence peak of Zn doped NWs was broaden compared to another samples. The luminescence origin of Zn, Si doped nanowires was investigated through variable temperature and power density PL tests (Fig.3-4). It was found out that, the optical performance of undoped and Si-doped nanowires is better seeing the luminescence origin is free exciton recombination (α＞1). However, the luminescence origin of Zn-doped nanowires is defect or impurity related transitions seeing its characteristic value α ＜ 1. Besides, its peak position is directly proportional to P^1/3, indicating the WZ/ZB II type luminescence. Combining with the TEM results, it can be further verified that, Zn-doped nanowires exhibited WZ/ZB mixed structure, which was the main cause of its larger full width at half maxima.

Conclusions This article used MOCVD technology and VLS growth mechanism to achieve epitaxial growth of silicon-based doped GaAs nanowires. Through SEM measurements, the nanowires were grown using the VLS growth mechanism and the growth direction is relatively disorderly. Through variable temperature and power density PL tests, it was found that the luminescence origin was free exciton recombination. The luminescence origin of Zn doped nanowires was defect or impurity related transitions along with the appearance of WZ/ZB II type luminescence. Based on TEM results, it can be concluded that due to the influence of Zn element, WZ/ZB mixed structure appear in Zn doped GaAs nanowires which complicated the luminescence mechanism of GaAs nanowires and added another radiation recombination. The appearance of WZ/ZB mixed structure caused the broadening of the low-temperature PL peak of Zn doped GaAs nanowires. The luminescence and structural properties of silicon-based doped GaAs nanowires was regulated by changing the doping source.