Experimental determination of deformation potentials and band nonparabolicity parameters for PbSe

Parabolic IV–VI multiple-quantum well structures were grown on ${\mathrm{BaF}}_2\mathrm{}\left(111\right)\mathrm{}$ substrates by molecular beam epitaxy and characterized by differential Fourier transform infrared transmission spectroscopy. To reduce unwanted Fabry–Perot interference fringes, the top surface of the parabolic MQW samples was coated with an antireflection film enabling unambiguous observation of subband transitions without superimposed interference fringes. Up to six principle quantized electron and hole transitions were observed. In contrast to III–V quantum well systems, the “forbidden” $\Delta n=2\mathrm{}$ quantum transitions are not observed in the IV–VI parabolic wells. Compared with the strain effect, the quantum size effect dominates the splitting of the degeneracy of the normal and oblique valleys at the L-point in the Brillouin zone. Intervalley splitting energies and the spacings of the principle energy levels in the parabolic wells allowed determination of the deformation potential constants for PbSe, $D_d=6.1\mathrm{}\mathrm{eV}$ and $D_u=-1.3\mathrm{eV}.$ From the fitting to the high-quantized energy levels observed in the differential transmission spectra, the nonparabolicity parameters for conduction and valence bands of PbSe are determined to be $1.9\times {10}^{-15}{\mathrm{cm}}^2.$