Monolithic Lateral p-n Junction GaAs Nanowire Diodes via Selective Lateral Epitaxy.

Semiconductor p-n junctions are essential building blocks of electronic and optoelectronic devices. Although vertical p-n junction structures can be formed readily by growth in sequence, lateral p-n junctions normal to surface direction can only be formed on specially patterned substrates or by post-growth implantation of one type of dopant while protecting the oppositely doped side. In this study, we report the monolithic formation of lateral p-n junctions in GaAs nanowires (NWs) on a planar substrate sequentially through the Au-assisted vapor-liquid-solid (VLS) selective lateral epitaxy (SLE) using metalorganic chemical vapor deposition (MOCVD). p-type and n-type segments are formed by modulating the gas phase flow of p-type (Diethylzinc) and n-type (disilane) precursors in situ during nanowire growth, allowing independent sequential control of p- and n- doping levels self-aligned in-plane in a single growth run. The p-n junctions formed are electrically characterized by fabricating arrays of p-n junction NW diodes with coplanar ohmic metal contacts and two-terminal I-V measurement. The lateral p-n diode exhibits a 2.15 ideality factor and a rectification ratio of ~106. The electron beam-induced current (EBIC) measurement confirms the junction position. The extracted minority carrier diffusion length is much higher compared to other published GaAs nanowires, suggesting a low surface recombination velocity in this lateral nanowire p-n diode.