New insights into the temperature-dependent photoluminescence of Mg-doped GaAs nanowires and epilayers

Abstract

The intentional introduction of impurities in semiconductor nanowires is very important in view of device applications. Doping affects the electronic energy level structure which in the case of III–V nanowires can also be strongly influenced by the simultaneous occurrence of two polytypes, zinc-blende (ZB) and wurtzite (WZ). In this work, we report a study on GaAs nanowires with different Mg-acceptor doping levels through temperature dependent photoluminescence. A comparable investigation is presented for Mg-doped GaAs epilayers. For the later, only a band is observed which is ascribed to the involvement of the Mg acceptor due to the observed bandgap energy narrowing effect with increasing the doping level, and the temperature dependent behaviour. A different behaviour is reported for nanowires: several radiative transitions are observed whose temperature dependence follows that of bulk GaAs, in accordance with spatially indirect recombination. Although the polytypic regions mask the role of doping in nanowires it favours the charge separation required for photovoltaic applications.