ANOMALOUS LUMINESCENCE PRESSURE-DEPENDENCE IN c-As₂S₃, a-As₂SeS₂: NATIVE DEFECT STRUCTURE.

The effect of compression on the sub-bandgap energy levels due to native defects in crystalline (c-) As//2S//3 and amorphous (a-) As//2SeS//2 is determined by hydrostatic pressure photoluminescence (PL) measurements to 108kbar at 13K. The main observation is a rapid decrease of the Stokes shift as the PL-energy, usually (P equals 0) at mid-bandgap, becomes more shallow. It is concluded that the PL-defects loosely couple adjacent layers (layer-fragments for the glass) in the ground state, and more tightly bond them in the excited state, thereby affecting a photo-induced local 2d yields 3d transition.