LUMINESCENCE AND FRANZ-KELDISH EFFECT ON CDTE(110)1X1 SURFACES BY SURFACE DIFFERENTIAL REFLECTIVITY

We present data on photoluminescence (PL) and the Franz-Keldish (FK) effect on ultra high vacuum cleaved CdTe(110)1 x 1 surfaces by surface differential reflectivity (SDR). PL and FK effects on the clean surface have been studied as a function of an argon laser power with the sample at room temperature. PL spectra have been divided into two contributions: a free excitons peak, which determines the PL peak position, and interband recombination structure, which dominates most of the PL spectra. A linear dependence of the area of the PL spectra on laser power confirms that the PL spectrum is mainly due to the contribution from the free-carrier recombination. The PL peak position shifts linearly towards lower energies (18 meV maximum) with increasing laser power, presumably due to local heating of the sample. The FK effect has an exponential dependence upon laser power. Upon switching off the laser, the FK effect disappears exponentially with a time constant of about 1300 s. Angle resolved photoemission has been used to evaluate the shift of the Fermi level upon laser irradiation. The FK and photoemission results are compared to evaluate the magnitude of the FK effect.