The high electric field properties of InP have been studied as a function of pressure to 55kbar. The measured threshold field for transferred electron instability showed an initial increase with pressure, and after passing through a maximum at 30-33kbar it decreased gradually. Monte Carlo calculations based on a stronger Γ-L scattering assumption seemed to agree better with the experimental data. The experimental results also indicated that a change from the two- to the three-level operation occurred near 30-33kbar.
Photoluminescence (PL) and optical absorption measurements on the heavily doped GaAs have been made as a function of pressure to 60kbar at 77K. With increasing pressure the spectrum shifted towards the higher energy side. The pressure dependence of the emission peak across the direct gap showed a noticeable change in slope at about 30kbar. For pressures above 35kbar the PL intensity suddenly decreased. The pressure dependence of the absorption edge in the heavily doped samples was quite different from that in the undoped or moderately doped samples. The observed behavior can be explained in terms of the effect of high doping on the inversion of the Γ and X conduction bands at high pressure.