CdZnTe Radiation Detectors with HgTe/HgCdTe Superlattice Contacts for Leakage Current Reduction

CdZnTe-based heterojunction p–i–n or M–π–n detectors using HgTe/HgCdTe superlattice contacts are modeled and designed to reduce leakage currents under high electric fields and thereby improve x-ray and γ-ray detector performance. The employment of an n-type HgTe/HgCdTe superlattice as a contact layer can theoretically result in significantly less leakage current compared with a contact layer using either bulk semiconductor or metal contacts. The benefits arise from the ability to design HgTe/HgCdTe superlattices to have large carrier effective masses in the electric field direction, which results in low carrier velocities. Nevertheless the density of states is lower than that of a comparable bulk semiconductor, which results in low carrier concentrations.