Incorporation of Be dopant in GaAs core and core–shell nanowires by molecular beam epitaxy

Abstract

Effective implementation of doped nanowires (NWs) in nanoscaled devices requires controlled and effective dopant incorporation. The one dimensional configuration of NWs poses a challenge for efficient doping due to the large number of surface states pinning the Fermi level close to the middle of the band gap and thus creating a large depletion layer at the surface. This effectively reduces the effective volume for doping. However, the flexibility of different architectures offered by the NWs, in particular, the core–shell configuration along with different growth mechanisms associated with the core and shell can be strategically used for efficient doping. In this work, the authors report on a catalyst free Ga-assisted approach for the growth of Be-doped GaAs NWs by molecular beam epitaxy. A systematic and a comprehensive study is reported using a variety of characterization techniques to determine the impact of NW configuration, Be cell temperature, and V/III beam equivalent pressure (BEP) ratio individually on doping incorporation in the NWs. Broadening of the photoluminescence spectra in the 1.49–1.51 eV range, as well as the longitudinal optical mode of the corresponding Raman spectra in combination with its red shift that is considered as a signature of higher Be incorporation, was found to occur for the core–shell configuration. Further, a lower V/III BEP ratio has a strong impact on enhancing the dopant incorporation.