Higher Voltage Ni/CdTe Schottky Diodes With Low Leakage Current

Abstract

A significant improvement in electrical characteristics of Schottky diodes designed for X-and-ray detectors has been achieved using semi-insulating CdTe single crystals and unified technology, where both Schottky and near-ohmic contacts were formed by the deposition of the same metal (Ni) on the opposite surfaces of the crystal pre-treated by chemical etching and Ar ion bombardment with different parameters. Reduction of injection of minority carriers from the near-ohmic contact in the neutral part of the diode and high Schottky barrier for holes provides low leakage current even at high bias voltage (50 nA cm 2 at 2000 V and at room temperature). The current-voltage characteristics of the detectors with Ni/CdTe/Ni electrode configuration in the low-voltage range are described by the generation-recombination Sah-Noyce-Shockley theory. The results of the reproducibility and time stability of the fabricated diodes are reported. Index Terms-Charge carrier processes, leakage currents, Schottky diodes, X-and gamma-ray detectors.

Mechanisms of Charge Transport and Photoelectric Conversion in CdTe-Based X- and Gamma-Ray Detectors

“…The Ni/CdTe/Ni diode structure with Schottky and near-Ohmic contacts at the CdTe(111)A and CdTe(111)B surfaces of semi-insulating CdTe single crystals (ρ = (2-4)•10 9 Ω•сm) demonstrates absence of rectification properties at bias voltages lower than 6-7 V, which can be attributed to a very high resistance of the CdTe substrate, that is, the voltage drop across the bulk part of the crystal should be taken into account. It should be noted that consideration of the voltage drop has strongly modified the shape of the forward I-V characteristic of the studied diode structure (Figure 5b) [21,23]. A sharp increase in the current at higher forward bias voltages is attributed to the injection of minority carriers from the Schottky contact into the neutral part of the crystal and the modulation of its electrical conductivity, which is confirmed by the results of calculations.…”

“…The theoretical analysis of experimental results allows identifying and explaining the essential features of the charge transport mechanisms depending on the resistivity of the material and the parameters of the diode structure, in particular the concentration of uncompensated impurities (defects) and the height of the potential barrier on Schottky contact [21]. According to the Sah-Noyce-Shockley theory, the current through the diode is determined by the integration of the generation-recombination rate over the whole space charge region (SCR) width [22].…”

Infrared LED Enhanced Spectroscopic CdZnTe Detector Working under High Fluxes of X-rays

“…The higher the photon flux of the 940-nm LED is, the higher is the amount of photogenerated electrons, resulting in a larger current flowing through the whole spectroscopic apparatus. This current contributes to the noise of the used electronics (e.g., amplifier) [20], which is reflected in the low energy part of the spectrum. For the 940-nm LED flux higher than $1.5\times {10}^{13}{\mathrm{mm}}^{-2}$·s${}^{-1}$, the photopeak completely disappeared due to the noise of the detector.…”

The COCAE Detector: An Instrument for Localization—Identification of Radioactive Sources

“…The electrical characteristics of the diodes were reported in [16], [17]. They exhibit pronounced rectification properties starting from the lowest voltages, while the reverse current at 800-1000 V is about two times lower than the best In/CdTe/Pt detectors and a steeper increase in the leakage current starts at higher voltages (at V instead of -V) [18].…”