Electrical Characterization of the Temperature Dependence in CdTe/CdS Heterojunctions Deposited In-Situ by Pulsed Laser Deposition

The I-V and C-V characteristics of CdTe/CdS heterojunctions deposited in-situ by Pulsed Laser Deposition (PLD) were evaluated. In-situ deposition enables the study of the CdTe/CdS interface by avoiding potential impurities at the surface and interface as a consequence of exposure to air. The I-V and C-V characteristics of the resulting junctions were obtained at different temperatures, ranging from room temperature to 150 °C, where the saturation current (from 10⁻⁸ to 10⁻⁴A/cm²), ideality factor (between 1 and 2), series resistance (from 10² to 10⁵ Ω), built-in potential (0.66-0.7 V), rectification factor (∼10⁶), and carrier concentration (∼10¹⁶ cm⁻³) were obtained. The current-voltage temperature dependence study indicates that thermionic emission is the main transport mechanism at the CdTe/CdS interface. This study also demonstrated that the built-in potential (V_{bi}) calculated using a thermionic emission model is more accurate than that calculated using C-V extrapolation since C-V plots showed a V_{bi} shift as a function of frequency. Although CdTe/CdS is widely used for photovoltaic applications, the parameters evaluated in this work indicate that CdTe/CdS heterojunctions could be used as rectifying diodes and junction field effect transistors (JFETs). JFETs require a low PN diode saturation current, as demonstrated for the CdTe/CdS junction studied here. © 2018 Author(s).