The photoluminescence and photoluminescence-excitation spectra of the isolated Zn vacancy, VZn, were measured under hydrostatic pressures of up to 50kbar at 7K. The photoluminescence band shifted, with pressure, some 30% faster than did the band-gap. Compression decreased the Stokes shift, thus reflecting a reduction in the C3v lattice relaxation around the VZn- site. Defect-molecule calculations showed that this arose from the predominance of spring-constant stiffening over increased Jahn-Teller coupling. Compression deepened the energy of the VZn- thermal level.

V.Iota, B.A.Weinstein: Physical Review Letters, 1998, 81[22], 4955-8