Electrical properties and electrical field in depletion layer for CZT crystals
(1.黑龙江省哈尔滨市哈尔滨工业大学材料科学与工程学院2.陕西省西安市西北工业大学材料科学与工程学院3.College of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China)
Abstract: 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 Em1=133 V/cm at x=0 for non-passivated CZT crystal and Em2=55 V/cm for passivated CZT crystal, respectively.
Key words: current-voltage characteristic; capacitance—voltage characteristic; depletion layer; electrical field