EMPTY SURFACE ELECTRONIC BANDS ON CDTE(110)

Angle-resolved inverse photoemission has for the first time been used to study the surface electronic band structure of a II-VI semiconductor, CdTe. The energy dispersion of an empty electronic surface state on CdTe(110), previously observed in normal emission only, has been mapped \ ̄gG-X̄ and \ ̄gG-X̄ ' in the surface Brillouin zone. In the course of this study new aspects of the surface electronic structure are observed. Firstly, we find two surface states with similar dispersions approximately 0.4 eV apart, one of which is the previously observed. Along \ ̄gG-X̄ ' they are both resonances but move into the projected bulk band gap along \ ̄gG-X̄ and become true surface states. Secondly, a rapidly dispersing structure is observed dispersing into the projected bulk band gap close to the X̄-point which we consequently identify as a third true surface state. These findings yield a new value for the surface band gap, located at \ ̄gG, of 2.9 eV. © 1990.