Deformation potentials of the fundamental exciton spectrum of InP

Wavelength-modulated reflectivity spectra are performed on the direct exciton spectrum of InP under uniaxialstress conditions. Working at liquid-helium temperature, both the fundamental ($E_0$) and spin-orbit split-off transition ($E_0+{\Delta }_0$) are investigated. For unstressed crystals, at 5 K the $1s$ excitons are found at 1418.2 ± 0.5 and 1526.3 ± 0.5 meV, respectively. The spin-orbit splitting energy (${\Delta }_0$) is found to be 108 ± 1 meV. Next the stress dependence in configurations $X$ parallel to the [001], [111], and [110] crystallographic axes are investigated. An inability to apply stress magnitudes larger than 3 kbar necessitates analyzing the data with a simple model of orbital-strain interaction which neglects the stress-dependent spin-orbit interaction. Three deformation potentials are deduced: A fully symmetric, interband, deformation potential $C_1+a_1=-8.0\mathrm{}\pm 0.4$ eV, which gives hydrostatic pressure coefficient $\frac{d{E}_0}{\mathrm{dP}}=11.1\mathrm{}\pm 0.6$ meV/kbar and two shear deformation potentials, $b=-2.0\mathrm{}\pm 0.2$ eV and $d=-5.0\mathrm{}\pm 0.5$ eV. The first one, associated with pure ${\Gamma }_{12}(2\mathrm{}{e}_{\mathrm{zz}}-e_{\mathrm{xx}}-e_{\mathrm{yy}})$ components of the strain tensor, gives the stress-induced splitting of the valence band under [001] compression while the second, associated with ${\Gamma }_{15}$ components, corresponds to pure [111] stress. The ratio of experimental splittings in both configurations is related to the anisotropic behavior of the valence band. For InP it is found to be about 0.7.