Spatially Resolved Optical Characterization of AlGaAs Layers Grown on Patterned Substrates

Abstract

We have applied micro-photoluminescence (PL) spectroscopy to scan the Al concentration and the well width of an undoped GaAs/AlGaAs single quantum well (QW) and micro-Raman spectroscopy to scan the carrier concentration of a Si-doped AlGaAs layer along (100)/(111)A/(100) facet transitions. The QW and the doped layer were grown by MBE on patterned GaAs substrates exhibiting (100) ridges and (100) grooves separated by 5 μm wide (111)A facets. The width of the GaAs QW, obtained from the spectral position of the QW PL, decreases from 10 nm on the (100) planes to 8 nm on the (111)A facet. The Al concentration, derived from the spectral position of the AlGaAs-barrier PL, varies between 23.5 and 29.5% along the facet transition. The type and concentration of charge carriers, deduced from the spectral position and line shape of the coupled plasmon–LO-phonon modes varies from n = 1.8 × 1018 cm—3 on the (100) planes to n < 4 × 1017 cm—3 or p-type on the (111)A facet.