Electrical properties and electrical field in depletion layer for CZT crystals

Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Au/p-CZT contacts with different surface treatments on cadmium zinc telluride (CZT) wafer's surface were measured with Agilent 4339B high resistance meter and Agilent 4294A precision impedance analyzer, respectively. The Schottky barrier height was 0.85 ± 0.05, 0.96 ± 0.05 eV for non-passivated and passivated CZT crystals by I-V measurement. By C-V measurement, the Schottky barrier height was 1.39 ± 0.05, 1.51 ± 0.05 eV for non-passivated and passivated CZT crystals. The results show that the passivation treatment can increase the barrier height of the Au/p-CZT contact and decrease the leakage current. The main reason is that the higher barrier height of Au/p-CZT contacts can decrease the possibility for electrons to pass through the native TeO2 film. Most of the applied voltage appears on the depleted layer and there is only a negligible voltage drops across the nearly undepleted region. Furthermore, the electric field in the depleted layer is not uniform and can be calculated by the depletion approximation. The maximum electric field of CZT crystals is E_m1=133 V/cm at x=0 for non-passivated CZT crystal and E_m2=55 V/cm for passivated CZT crystal, respectively.