Si doping effects on (In,Ga)N nanowires

Abstract

Si doped (In,Ga)N nanowires (In content up to 0.4) are grown on Si(111) substrates by plasma-assisted molecular beam epitaxy. By increasing the Si doping level, coalescence between nanowires is reduced and a more uniform morphology is obtained. The Raman spectra from highly doped samples show a characteristic broad band in the optical phonon frequency range, which became more prominent at higher doping levels. This Raman band can be explained by plasmon-phonon scattering from a free electron gas with strong wave-vector nonconservation, providing evidence for successful n-type doping. The measured plasmon-phonon modes are explained by lineshape simulations taking into account the simultaneous contribution of both the charge-density fluctuation and the impurity induced Fröhlich scattering mechanisms. The according lineshape analysis allows for an estimate of the carrier concentration.