Pressure dependence of the direct absorption edge of InP

Abstract

The variation of the lowest direct absorption edge of InP with pressure has been measured at room temperature with a diamond anvil cell for pressures up to the phase transition (100 kbar). Both transmission and luminescence techniques were used. The gap varies sublinearly with pressure but linearly with lattice constant: the gap deformation potential so obtained is $a=-6.35\mathrm{}\pm 0.05$ eV. This result is discussed in the light of theoretical calculations. The observed luminescence intensity remains nearly constant as a function of pressure up to 90 kbar. At this pressure the efficiency begins to decrease thus signaling the crossing of the $\Gamma$ and $X$ conduction-band minima which we estimate to occur at 104 ± 1 kbar. The pressure coefficient of the $\Gamma -X$ indirect gap is found to be -(3 ± 1) × ${10}^{-6\mathrm{}}$ eV/bar.