Cathodoluminescence mapping of electron concentration in MBE-grown GaAs:Te nanowires

Abstract

Cathodoluminescence mapping is used as a contactless method to probe the electron concentration gradient of Te-doped GaAs nanowires. The room temperature and low temperature (10 K) cathodoluminescence analysis method previously developed for GaAs:Si is first validated on five GaAs:Te thin film samples, before extending it to the two GaAs:Te NW samples. We evidence an electron concentration gradient ranging from below 1 x 1018 cm-3 to 3.3 x 1018 cm-3 along the axis of a GaAs:Te nanowire grown at 640 °C, and a homogeneous electron concentration of around 6 - 8 x 1017 cm-3 along the axis of a GaAs:Te nanowire grown at 620 °C. The differences in the electron concentration levels and gradients between the two nanowires is attributed to different Te incorporation efficiencies by vapor-solid and vapor-liquid-solid processes.

GaAs/GaInP nanowire solar cell on Si with state-of-the-art Voc and quasi-Fermi level splitting

“…Semiconductor doping is key to functional p-n junctions, however the introduction of dopants during NW growth greatly affects the thermodynamics and kinetics of the system often resulting in axial and radial doping gradients in NWs. [39][40][41][42][43] Doping compensation mechanisms can also prevent high doping concentrations to be achieved, [44][45][46] rendering surface passivation essential for most III-V NWs. This is important for GaAs NWs as they are particularly prone to surface depletion due to high surface recombination velocity.…”