Band alignments and strain effects in PbTe/Pb1?xSrxTe and PbSe/Pb1?xSrxSe quantum-well heterostructures
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The optical transitions and band alignments of PbTe/Pb1?xSrxTe and PbSe/Pb1?xSrxSe multi-quantum-well heterostructures were studied using temperature-modulated absorption spectroscopy and envelope function calculations. By taking advantage of the strain-induced splitting of conduction- and valence-band states at the different L points of the Brillouin zone, a reliable determination of the band offsets is obtained, taking into account the biaxial strain of the quantum wells derived by x-ray diffraction. Through this analysis, the normalized conduction-band offsets are determined as ?Ec/?Eg=0.45±0.05 for the PbTe/Pb1?xSrxTe system and 0.6±0.1 for the PbSe/Pb1?xSrxSe system for Sr contents up to 13%. Within the experimental precision, the band offsets are independent of temperatures from 20?300 K. With these parameters, precise modeling of the energy levels and optical transitions is achieved as required for optoelectronic device applications.