Search

The effects of hydrogen treatment on electrical properties of detector-grade cadmium manganese telluride (CdMnTe:In) crystals were investigated. The results showed that the resistivity of the crystals was improved from $10^{9}$ to $10^{10} ~\Omega \cdot $ cm after annealing. With the increase of annealing time, the resistivity first increased and then decreased. Hydrogen passivation reduced the carrier concentration and enhanced mobility. The disappearance of A1 phonon mode of Te in Raman spectroscopy suggested that Te was decreased in crystal surface. The energy resolution and mobility–lifetime product of CdMnTe detectors were significantly improved. The CdMnTe:In crystal annealed for 30-h hydrogen treatment with greatest energy resolution and highest ( $\mu \tau $ )e value had the best detector performance.

In this paper, CdMnTe nanopowders with uniform shapes were prepared through a facile hydrothermal route using 3-mercaptopropionic acid (MPA) as the stabilizer and modifier. The effects of different experimental conditions including Cd-to-MPA ratio, pH value and reaction temperature on the phase composition and formation mechanism of as-prepared nanopowders were studied. XRD results indicated as-prepared CdMnTe nanopowders were pure phase and had cubic sphalerite structure with high crystallinity. SEM and Rietveld refinement clearly showed that the powders were about 10-100 nm in size. In PL measurement, there was a strong luminescence peak in the infrared region 1.717-1.826 eV. Compared with the CdMnTe single crystal, a blue shift of about 0.109 eV indicated a wider band gap. In UV-vis spectra, the absorption peak of the sample blue shifted with the decrease of crystal size, which indicated an obvious quantum confinement effect (QCE) in nanopowders. The optimal conditions for the preparation of CdMnTe nanopowders are 180 °C for 24 h with the molar ratio 1 : 1 of Cd : MPA at pH 13. In particular, the growth kinetics and possible formation mechanism of the nanopowders were proposed.

In this paper, the effects of Te inclusions on the optical and electrical properties of CdMnTe and CdMgTe crystals grown by the modified vertical Bridgman method were investigated. For CdMnTe ingot, the average size and density distribution of Te inclusions along axial direction were in the range of 12 ~ 29 μm and 1.53 × 104 cm−2 ~ 2.81 × 105 cm−2, respectively. For CdMgTe ingot, the average size and density distribution of Te inclusions were in the range of 6 ~ 20 μm and 8.17 × 103 cm−2 ~ 2.42 × 104 cm−2, respectively. The density and size of Te inclusions increased gradually from the first-to-freeze part to the last-to-freeze part for CdMnTe ingot, while that of CdMgTe ingot first decreased and then increased. For both CdMnTe and CdMgTe ingots, the resistivity, IR transmittance and FWHM of (D0, X) peak first increased and then decreased from the first-to-freeze part to the last-to-freeze part. The middle-to-freeze parts of both ingots had the best crystal quality. For both CdMnTe and CdMgTe detectors, the energy resolution and (μτ)e value were first increased and then decreased from the first-to-freeze part to the last-to-freeze part. The detectors fabricated by the middle-to-freeze parts of both crystals had the best performance and can could meet the requirements of room temperature radiation detection. PACS: 78.30.Fs; 78.55.Et; 81.40.Ef.

Temperature-dependent photoluminescence (PL) properties of indium-doped CdMnTe (CMT:In) crystals were investigated. Four emission peaks of the tip crystal and three emission peaks of the tail crystal from as-grown CMT:In ingot were observed at low-temperature (10 K) PL spectra, respectively. From 20 K to 40 K, PL intensity of the deep defect-related emission peak (Dcomplex) increased with temperature, showing a negative thermal quenching effect for the tip crystal. Interestingly, from 60 K to 80 K, negative thermal quenching phenomena were found for three emission peaks, the neutral donor–bound exciton (D0,X), the donor–acceptor pair DAP and Dcomplex, in PL spectra of the tail crystal. ICP-MS test, IR transmittance, I–V measurement and IR microscope revealed that the CMT:In crystals with many impurities and defects tended to cause abnormal photoluminescence. Specially, impurities mainly resulted in the formation of intermediate states and were responsible for the negative thermal quenching behavior. The abnormal PL behavior can be explained by intermediate states.