Monolithic lateral p–n junction GaAs nanowire diodes via selective lateral epitaxy

Abstract

Semiconductor p–n junctions are essential building blocks of electronic and optoelectronic devices. Although vertical p–n junction structures can be formed readily by growing 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 selective lateral epitaxy using metalorganic chemical vapor deposition. 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 measurements. The lateral p–n diode exhibits a 2.15 ideality factor and a rectification ratio of ∼106. The electron beam-induced current measurement confirms the junction position. The extracted minority carrier diffusion length is much higher compared to those previously reported, suggesting a low surface recombination velocity in these lateral NWp–n diodes.