## Surface State Stabilization Before Electrode Deposition
When passivation is applied before electrode deposition, it stabilizes and chemically modifies the CdZnTe surface by saturating dangling bonds, reducing surface defect states, and removing surface contaminants. This creates a more chemically inert and electrically stable interface. Depositing electrodes on this well-passivated surface prevents the formation of additional surface states or defects that could arise from direct metal-semiconductor interaction, thereby reducing pathways for leakage current.
## Prevention of Metal-Induced Surface Defects
Direct deposition of electrodes onto an unpassivated CdZnTe surface can induce damage or introduce interface states due to the interaction between the metal atoms and the semiconductor surface. This can create localized regions with increased conductivity or trap states that facilitate leakage current. By passivating first, the surface is protected from such metal-induced damage or defect formation, minimizing the creation of low-resistance leakage paths.
## Formation of a Uniform and Controlled Interface
Passivation layers help produce a uniform surface chemistry and morphology. When electrodes are subsequently deposited on this uniform surface, the metal-semiconductor interface is more controlled and consistent. This uniformity reduces localized electric field enhancements or irregularities that might otherwise lead to leakage current through localized tunneling or shunting paths.
## Improved Barrier Properties at the Metal-Semiconductor Interface
Passivation can modify the surface electronic properties, such as work function and band bending, which influence the Schottky barrier height at the electrode-semiconductor junction. Depositing electrodes after passivation ensures that the barrier is well-defined and higher, which effectively blocks carrier injection under reverse bias, reducing leakage current. Without passivation, uncontrolled interface states may lower the barrier and increase leakage.
## Reduced Surface Contamination and Residual Charges
Passivation often includes cleaning and chemical treatment steps that remove surface contamination like oxides, adsorbates, or residues. When electrodes are deposited afterward, these contaminants are minimized, reducing unintentional conductive paths and charge traps that cause leakage current.
## Summary
Depositing electrodes after passivation reduces leakage current more effectively in CdZnTe devices because the passivation stabilizes and cleans the surface, prevents metal-induced defect formation, promotes uniform interfaces, improves the Schottky barrier at the metal-semiconductor junction, and minimizes conductive pathways that contribute to leakage. This sequence results in devices with lower dark current, improved electrical characteristics, and enhanced performance.
CdZnTe Association (CdZnTe.com)
https://www.cdznte.com/blog/why-does-depositing-electrodes-after-passivation-reduce-leakage-current-more-effectively-in-cdznte-devices.html
