Deformation Potentials of the Indirect and Direct Absorption Edges of AlSb

The splittings and shifts of the phonon-aided indirect exciton edge (${\Gamma }_{15}\to X_1$) of AlSb produced by uniaxial stresses along [001], [111], and [110] have been determined. These measurements were performed at 77°K, using the wavelength-modulation technique. TO-phonon-assisted transitions, not reported previously, have been identified in the spectrum of the stressed materials; they yield a TO-phonon energy at $X$ of 42±3 meV. These measurements have also yielded the shear deformation potentials of the ${\Gamma }_{15}$ valence band ($b=-1.35\mathrm{}\pm 0.1$ eV and $d=-4.3\mathrm{}\pm 0.4$ eV) and the $X_1$ conduction band (${\mathcal{E}}_2=+5.4\mathrm{}\pm 0.3$ eV). The hydrostatic deformation potential of the indirect edge was found to be $a_i=+2.2\mathrm{}\pm 0.2$ eV. Electroreflectance measurements at room temperature of the direct edge (${\Gamma }_{15}\to {\Gamma }_{1c}$) of this material under uniaxial compression along the [110] direction have also been performed. The stress-induced splitting of the ${\Gamma }_{15}$ band observed in these measurements agrees with that obtained from the indirect exciton. The hydrostatic coefficient of the direct edge was found to be -5.9±1.2 eV.