SHIFTING PHOTOLUMINESCENCE BANDS IN HIGH-RESISTIVITY LI-COMPENSATED GAAS

It is shown that Li diffusion of GaAs can give rise to semi-insulating samples with electrical resistivity as high as 10(7) OMEGAcm in undop ed, n-type, and p-type starting materials. The optical properties of t he compensated samples are correlated with the depletion of free carri ers caused by the Li diffusion. The radiative recombination of the Li- compensated samples is dominated by emissions with excitation-dependen t peak positions that shift to lower energies with increasing compensa tion. The photoluminescence properties are characteristic of fluctuati ons of the electrostatic potential in strongly doped, compensated crys tals.