Optoelectronic Devices

Copper halides have been studied for several decades [1-3] but the importance of IB-VIIA semiconductors are still growing because of the potential applications occurring from the restricted excitons in micro-crystals made of these materials [4]. The copper halides crystallize in the zinc blend lattice (space group F-43m) and are tetrahedral coordinated semiconductors. Cu atom is located at position (0, 0, 0), while X (F, Cl, Br, I) atoms are located at (1/4, 1/4, 1/4) positions. The electronic configuration of zinc blend structure is derived from sp3-sp3 configuration while the valence bands of copper halides are due to sp3-sd3. As a result of the pd hybridization considerably changes physical properties of copper halides are considerably different compared with other members of ANB8-N series. B. Amrani et al [5] performed under pressure calculations on these materials and found that they transform from the zinc-blend (B3) to the rocksalt (B1) structure. Experimental studies [6-8] have revealed that CuCl, CuBr and CuI adopt the rocksalt structure at a pressure around in the region of 10 GPa, though the zinc blende-rocksalt transition occurs via several intermediate structures of lower symmetry. According to Amrani et al, the most interesting feature of the copper halides is the occurrence of a filled d10-shell.

In this work, the adopted method of the CdSe doped with Cu (CdSe: Cu) photodetector is presented. This detector is prepared by vacuum evaporation of CdSe films on a glass substrate followed by vacuum annealing under an argon atmosphere for doping with copper. The detector is found, for the first time, to cover a wide range of the infrared besides the visible region of the electromagnetic spectrum. This finding of the wavelength tuning is due to the localized energy states of copper atoms inside the band gap of the CdSe. These characteristics stem from the unique band structure of CdSe: Cu. This tuning is compared with recent work in the corresponding colloidal CdSe-ZnS core shell quantum dots and with the quantum well (QWIR) and quantum dots infrared detectors (QDIR). The major significance of this developed detector is in its synthesis simplicity and its fabrication processes costs in comparison with that of the (QWIR) and (QDIR) detectors. The structural analysis results demonstrated that the vacuum annealing in competition with the doping concentration improves significantly the film structure. A better crystalline structure is reported at 5 wt% of Cu concentration and at annealing temperature of 350ºC. Besides the measured specific detectivity at room temperature is D*=2.31×10 8 cm Hz 1/2 W-1. This value approaches the detectivity of the state of art mercury cadmium telluride (MCT). This result paves the way for further investigations and improvements.