Antimonide Nanowires for Multispectral Infrared Photodetection

Abstract

Multispectral capabilities of nanowires (NWs) were explored for InAs and InAsSb NWs on Si(111) substrates. NWs were grown with the vapour-solid (VS) growth mode in a molecular beam epitaxy (MBE) system using an oxide template to control positions and diameters. Early attempts to integrate InSb NWs and silicon substrates proved unsuccessful. Instead studies of InAs NWs on silicon, and eventually InAsSb/InAs NWs on silicon were completed to achieve large-diameter, infrared (IR) sensitive photodetectors. InAs NWs were grown on silicon substrates to study their morphology characteristics and vertical NW yield. The five different growth modes explored were (1) Au-assisted vapour-liquid-solid (VLS), (2) positioned Au-assisted, (3) vapour solid, (4) positioned Au-assisted VLS using a patterned oxide mask (VLS-SAE), and (5) selective area epitaxy (SAE) using a patterned oxide mask. Optimal temperature and V/III flux ratios for achieving a high vertical yield were found for the SAE growth mode. Further understanding of the InAs SAE growth mode was gained through modeling of various oxide hole filling scenarios. Each scenario was defined by the arrival rates of the group III and group V materials to the holes. A parameter space is discussed for the growth of high yield InAs NWs, dependent on the V/III flux ratio and temperature of growth. Large diameter InAsSb NWs for IR absorptance were grown on silicon using a high yield InAs stem. Several NW array diameters were grown simultaneously on the same substrate to measure multispectral photodetection. Diameters were controlled by NW spacing. Fourier transform IR (FTIR) spectroscopy was used to measure absorptance in the NWs. NW diameters spanned 440 – 520 nm which resulted in enhanced absorptance in the short-wave IR region. Simulations of the HE11 resonances of the NW arrays were performed and compared with the FTIR measurements. Initial electrical measurements demonstrated a diameter-dependent photocurrent.