Studies of Be, Si doping regulated GaAs nanowires for phase transition and optical properties

Abstract

GaAs-based semiconductor doping technology, in which impurity energy levels are introduced into the band gap, can give rise to a decisive effect on its electrical and optical properties. When GaAs material is reduced to one-dimensional nanoscale, due to the increase of specific surface area, wurtzite- zinc blende coexisting structure is prone to appearing. GaAs nanowire doping can not only adjust its electro-optical properties, but also have a significant regulatory effect on its structural phase transition. The effects of beryllium (Be) and silicon (Si) doping on crystal structure and optical properties of gallium arsenide (GaAs) nanowires (NWs) are studied in this paper. Primitive, Si-doped and Be-doped GaAs NWs are grown on Si(111) substrates by molecular beam epitaxy in virtue of the self-catalyzed growth mechanism. The Raman spectra of primitive, Si-doped and Be-doped GaAs NWs are measured. The E2 mode peak unique to the WZ structure of primitive GaAs NWs is found in the Raman spectrum, and the E2 mode peak in the Raman spectrum of Si-doped GaAs NWs weakens or even disappears. Moreover, The E2 mode peak is not found in the Raman spectrum of Be-doped GaAs NWs. Furthermore, the structural changes of GaAs NWs are observed more intuitively by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The PL spectra show that the wurtzite (WZ)-zinc blende (ZB) mixed phase II-type luminescence exists in primitive GaAs NWs, then the luminescence disappears due to Si or Be doping and turns into impurity defect related luminescence.