Carrier emission from quantum wells and from deep-level defects was studied by means of deep-level transient spectroscopy. The emission from quantum wells contributed to a majority carrier peak, from which the valence-band offset at the hetero-interface could be derived. In the case of Si0.67Ge0.33/Si, the offset of 0.24eV was comparable with theoretical predictions and with previous measurements. The emission of carriers from a high density of interfacial defects gave rise to a minority carrier signal, in deep-level transient spectroscopy, which could be detected only by using an injection pulse with a relatively large width. Partial relaxation of the misfit strain, or the nucleation of dislocations, was suggested to be responsible for the formation of interfacial defects.

Q.Wang, F.Lu, D.Gong, X.Chen, J.Wang, H.Sun, X.Wang: Physical Review B, 1994, 50[24], 18226-30