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

Abstract

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–Schrödinger 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.