Emergence of deep levels in n-type ZnSe under hydrostatic pressure.

Photoluminescence is measured in n-type ZnSe doped with Ga and Cl under pressures to 100 kbar (at 7 K). For each dopant, the rate of pressure shift of the self-activated band changes at 25–30 kbar from faster than to slower than that of the band gap. The change is evidence that a previously unknown deep donorlike state emerges from the electron continuum. This state probably is related to zinc vacancydonor complexes, whose levels move lower in the gap with compression.