Silicon doping effects on optical properties of InAs ultrathin layer embedded in GaAs/AlGaAs:δSi high electron mobility transistors structures

Micro-Raman scattering measurements were used to study the silicon delta-doped layer density variation effect on InAs ultrathin layer embedded in silicon-delta-doped GaAs/AlGaAs high electron mobility transistors (HEMTs) structures properties. These structures were grown by molecular beam epitaxy on GaAs substrates with different silicon (Si) delta-doped layer densities. Two coupled plasmon-longitudinal optical (LO) phonon modes (L and L+) were observed in the micro-Raman spectra of the Si-delta-doped samples, and both their wave numbers and intensities were dependent on the silicon delta-doped layer density. There is evidence to suggest that the increase of the Si doping level results in the increase of exciton-phonon scattering which is mainly due to the incorporation of Si and the increase of the two-dimensional electron gas (2DEG) in the InAs/GaAs interface. From fitting the temperature-dependence of full width at half maximum (FWHM) of quantum well's photoluminescence peak (P-1) by the exciton-photon coupling model, it was found that the interaction between exciton and phonon in Si-delta-doped quantum wells was higher than that in the undoped sample. This result was confirmed as resulting from the increase of plasmon-phonon scattering which is attributed to the increase of free carriers donated from implanted Si dopant. The self-consistent Poisson-Schrodinger model calculation results are in good agreement with the experimental results, where the 2DEG densities increase linearly with increasing the Si-delta-doped layer density. (C) 2011 Elsevier Ltd. All rights reserved.