OBSERVATION OF LUMINESCENCE AND FRANZ-KELDISH EFFECT ON CLEAVED CDTE(11O) SURFACES

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 the FK effect on a clean surface have been studied as a function of argon laser power with the sample at room temperature. PL spectra have been deconvoluted into two contributions: a free exciton peak, which determines the PL peak position, and an interband recombination structure, which dominates most of the PL spectra. The linear dependence of the area of the PL spectra on laser power confirms that the PL spectrum is mainly due to the contribution from free-carrier recombination. The PL peak position shifts towards lower energies (18 meV maximum), linearly 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 exponentially disappears 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. FK and photoemission results are compared to evaluate the magnitude of the FK effect. Moreover, the photovoltage induced by the photoemission lamp has been measured through the FK effect and resulted to be 80 meV.