HgCdTe/CdZnTe p-i-n high-energy photon detectors

Classical solid-state detection of x-ray and gamma-ray radiation consists of a high voltage applied between two metallic contacts sandwiching a high resistivity, high dielectric strength material; high voltage and high resistivity are required to enable complete charge collection while minimizing the resolution-degrading leakage current (dark current). We report here the conception and successful fabrication and test of a new device construct which changes this paradigm. P-type and n-type layers are fabricated by mercury cadmium telluride (HCT) liquid phase epitaxy (LPE) on opposite sides of a high-quality wafer of CdZnTe (CZT) in order to construct a p-i-n diode structure. Wafers up to 9 cm(2) area have been grown. This diode structure provides an extremely high effective resistivity and barrier to the flow of dark current in the device. Several wafer lots have repeatably yielded p-i-n detectors which exhibit typical diode current-voltage (I-V) curves with very low dark currents at very high bias voltages. Spectra obtained from these detectors produce exceptionally sharp photopeaks which exhibit very little low-energy tailing.