Optical absorption edge of compensated germanium

The optical absorption of heavily doped and closely compensated Ge is calculated using a Halperin-Lax band-tail model and an ad hoc matrix element. The only adjustable parameter is an effective temperature Tion for the contribution of the position correlations of the ions to the screening; Tion is estimated to be about 7000°K. The results are in reasonable agreement with experiment; direct transitions at k=0 make the dominant contribution to the edge. © 1971 The American Physical Society.