INVESTIGATION OF THE BAND-STRUCTURE OF THE STRAINED SYSTEMS INGAAS-GAAS AND INGAAS-ALGAAS BY HIGH-PRESSURE PHOTOLUMINESCENCE

In(x)Ga1-xAs quantum wells grown pseudomorphically in GaAs and AlGaAs with values of x up to 0.25 have been studied by photoluminescence under high hydrostatic pressure. We concentrate here on the pressure range where the emissions quench and take on the characteristics of the X-minima. In the InGaAs/GaAs structures, these transitions display an unexpected pressure coefficient, -2.6 meV/kbar, twice that of the X minima in GaAs. We assign these transitions to the X minima in the wells, and therefore make a direct measurement of the strained X positions as a function of composition. In the InGaAs/AlGaAs structures the crossovers occur against the X-minima in the barriers and these crossovers yield an accurate value for the band offset ratio for InGaAs/GaAs heterojunctions which is found to be 60:40 (CB:VB).