Electrical and optical evaluation of n-type doping in In _x Ga_(1-x)P nanowires

To harvest the benefits of III-V nanowires in optoelectronic devices, the development of ternary materials with controlled doping is needed. In this work, we performed a systematic study of n-type dopant incorporation in dense In _x Ga_(1-x)P nanowire arrays using tetraethyl tin (TESn) and hydrogen sulfide (H₂S) as dopant precursors. The morphology, crystal structure and material composition of the nanowires were characterized by use of scanning electron microscopy, transmission electron microscopy and energy dispersive x-ray analysis. To investigate the electrical properties, the nanowires were broken off from the substrate and mechanically transferred to thermally oxidized silicon substrates, after which electron beam lithography and metal evaporation were used to define electrical contacts to selected nanowires. Electrical characterization, including four-probe resistivity and Hall effect, as well as back-gated field effect measurements, is combined with photoluminescence spectroscopy to achieve a comprehensive evaluation of the carrier concentration in the doped nanowires. We measure a carrier concentration of ∼1 × 10¹⁶ cm^-3 in nominally intrinsic nanowires, and the maximum doping level achieved by use of TESn and H₂S as dopant precursors using our parameters is measured to be ∼2 × 10¹⁸ cm^-3, and ∼1 × 10¹⁹ cm^-3, respectively (by Hall effect measurements). Hence, both TESn and H₂S are suitable precursors for a wide range of n-doping levels in In _x Ga_(1-x)P nanowires needed for optoelectronic devices, grown via the vapor-liquid-solid mode.