Investigation of Charge Transport in CdTe Detectors Using Edge-Transit Current Technique

This study explores the charge transport properties of Cadmium Telluride detectors, employing the transient current technique with red laser light with a beam waist of $6 \mu \mathrm{m}$ FWHM. The beam was aligned parallel to the detector surface and perpendicular to the metal electrodes to generate electron-hole pairs at known depths. The CdTe crystals were configured into a planar diode structure with Titanium on the Tellurium-terminated side and Gold on the Cadmium-terminated side, creating a Schottky barrier. The dimensions of the samples were $3 \times 3 \times 0.95 \mathrm{~mm}$, with equal metallization of $2.5 \times 2.5 \mathrm{~mm}$ on both sides. Our study systematically varied the laser beam’s position to modulate the depth of carrier generation and applied different voltages, including both polarities at the tellurium-terminated electrode which served as the collection electrode. Charge movement through the bulk and across crystalline defects was reconstructed, and electrical field profiles were determined from recorded waveforms. Via the Hecht equation the $\mu \tau$ product was extracted. Our findings provide insights into the mechanisms of charge transport and the impact of structural anomalies on detector performance.