Diodes based on semi‐insulating CdTe crystals with Mo/MoO_x contacts for X‐ and γ‐ray detectors

Abstract

This paper reports on the possible applications of molybdenum oxide (Mo/MoOx) contacts in combination with semi‐insulating CdTe crystals. The electrical contacts to p‐type Cl‐doped CdTe crystals were formed by the deposition of molybdenum oxide and pure molybdenum thin films by the DC reactive magnetron sputtering. Electrical properties of the prepared Mo‐MoOx/р‐CdTe/MoOx‐Mo surface‐barrier structures were investigated at different temperatures. It is shown that the rapid growth of the reverse current with increasing bias voltage higher than 10 V is caused by the space‐charge limited currents. Spectrometric properties of the Mo‐MoOx/р‐CdTe/MoOx‐Mo structures have been also analyzed. It is revealed that the developed heterojunction has shown promising characteristics for its practical application in X‐ and γ‐ray radiation detector fabrication.

CdTe Based X/γ-ray Detector with MoOx Contacts

“…In this work we continue the investigation of the gamma response of MoOx/р-CdTe/MoOx-Mo detectors studied in Ref. [5]. Using different methods of ion etching of CdTe crystals prior deposition of MoOx contacts the dark current of the detectors has reduced and, as a consequence, its spectrometric properties have significantly improved.…”

“…2, detector 2). The full width at half maximum (FWHM) of the peak amounts to 6.58 keV, which corresponds to 11.05 % of the photon energy of radiation emitted with a 241 Am isotope [5]. Further optimization of the MoOx film deposition conditions, namely, changing the stoichiometric composition of the film and the sputtering time (partial pressure of argon and oxygen in the vacuum chamber were 0.24 and 0.024 Pa, respectively, and the processing time of ~ 60 s), led to a decrease by an order of magnitude the reverse current density at bias voltage of 40 -60 V (Fig.…”

“…However a rapid growth of the leakage current with increasing bias is often observed due to the currents limited by the space charge. The origin of the excess charge carriers can be either tunneling of charge carriers through a thin insulating film between the crystal and the metal contact [4] or injection of minority carriers from imperfect Ohmic contact on the opposite face of the crystal [5]. Therefore, the problem of forming noninjecting contacts to CdTe is actual scientific and technical problem.…”

CdTe X/γ-ray Detectors with Different Contact Materials

“…During the last two decades, we have widely used semi-insulating CdTe semiconductors, produced by Acrorad for material characterization [15][16][17] and elaboration of both Schottky diode-type [18][19][20][21][22][23][24][25][26][27] and M-p-n structured [27][28][29][30][31][32][33][34] X/γ-ray detectors. Using different metals (Ni, Cr, In, Al, and Au) for electrodes to form appropriate Schottky and ohmic electrical contacts or employing laser-induced doping of a thin CdTe layer with In, we have obtained high performance diode-type X/γ-ray detectors with excellent roomtemperature energy resolution.…”

“…We have recently studied other electrode materials (graphene, metal oxides and nitrides) different from metals used before and developed the techniques to employ them for the formation of Schottky and ohmic electrical contacts to Acrorad's semi-insulating CdTe crystals [21][22][23][24][25][26]. We have interested to develop this trend, in particular using molybdenum oxide as a promising material for ohmic contact formation [35][36][37][38][39][40].…”