The dependence of structural, optical and electrical properties on substrates for GaAs nanowires grown by metal organic chemical vapor deposition.

GaAs nanowires (NWs) play important roles in the field of low-dimensional infrared photodetector and laser. In this work, the GaAs NWs are directly grown on Al 2 O 3 , Si and SiO 2 substrates by metal organic chemical vapor deposition. The structural, optical and electrical properties of these NWs are further studied to reveal the effect of substrates. Using transmission electron microscopy characterization, the wurtzite/zinc-blend (WZ/ZB) mixed-phase structure and plenty of defects are directly observed in the GaAs NWs grown on Si and SiO 2 substrates. But the GaAs NWs grown on Al 2 O 3 substrates are high-quality, uniform and single-phase. The peak shapes of the photoluminescence (PL) spectra of the three samples are quite different, which is essentially attributed to the structural difference. Temperature- and power-dependent PL spectra are performed to analyze the origin of peaks. The luminescence of GaAs NWs on Al 2 O 3 substrate originates from exciton related recombination, while that of the GaAs NWs on Si and SiO 2 substrates come from free exciton emission, the defect-related emission and the radiative recombination at the WZ/ZB mixed-phase interface. The electron mobility of GaAs NWs on Al 2 O 3 substrate is higher than that on Si and SiO 2 substrates, which is due to the small carriers scattering of pure phase nanowires. This work has a great influence on the fabrication of GaAs NWs and their application in optoelectronic devices. [ABSTRACT FROM AUTHOR]