Ji Jun Zhang

Effects of the Substrate Temperature on the Structure and Properties of Cd1-xMnxTe Films

Cd1-xMnxTe (CdMnTe) can be a good candidate for gamma and X-ray detection because of its wide band-gap, high resistivity, and good electro-transport properties. Polycrystalline CdMnTe films were grown by closed-space sublimation method on glasses at different substrate temperatures. In this paper, substrate temperature dependent surface morphology, chemical composition, structural and electrical properties of CdMnTe films are investigated systematically.

Growth of ZnS Films and Application in Heterojunction

ZnS films were prepared by radio-frequency (RF) magnetron sputtering method. The effects of substrate temperature and annealing treatment on the properties of ZnS films were studied. The ZnS films were characterized by X-ray diffraction (XRD), UV-visible spectrophotometer, and electrical measurements. The results showed that the higher substrate temperature and post-deposition annealing treatment was helpful in improving the crystalline quality of the films, and the film had an n-type conductivity. N-type ZnS films were also deposited on p-type single-crystalline silicon (Si) substrates to fabricate ZnS/ Si heterojunction. The current-voltage (I-V) characteristic of the heterojunction was examined, which showed a rectifying behavior with turn-on voltage of about 2V.

Properties of CdMnTe Single Crystal Used in Nuclear Radiation Detectors

The Cd1-xMnxTe crystal is believed to be a good candidate to compete with Cd1-xMnxTe in the X-ray and γ-ray detector application. In this paper, Indium (In) doped Cd0.8Mn0.2Te (CdMnTe) ingots were grown by the modified Vertical Bridgman method. The as-grown crystals were characterized using Near-Infrared (NIR) transmission spectrum mapping of composition, X-ray double-crystal rocking curve measurement, I-V measurement and 241Am gamma rays radiation measurement. The Mn composition extracted from the NIR spectra at different axial and radial distances of the 30×40×2 mm3 CdMnTe wafers shown that the Mn concentration in the range of 0.19430.0008 to 0.2020.0025 mole fraction. The FWHM values of the X-ray rocking curves are of 40-80 arc sec, indicating a high crystalline perfection. The resistivity of the wafers is (2-3) ×1010Ω.cm. The CdMnTe planar detector irradiated by 241Am source shows the energy resolution of 8.5%.

Te Inclusions in CdMnTe Crystal Grown by the Traveling Heater Method and their Effects on the Electrical Properties

The concentration and size distribution of Te inclusions in CdMnTe (CMT) are key factors in nuclear devices performance. High-concentration and large-size Te inclusions degrade the performance drastically, especially for electrical properties. In this paper, the Te inclusions along the axial and radial directions in CMT crystal grown by the Traveling Heater Method (THM) were revealed by Infrared Microscopic System. The size of Te inclusions is 5-17 μm and the concentration is (2.5-4.6) ×105 cm-3. The Current-Voltage measurements were performed and the resistivity of the CdMnTe crystal with excess Te was in the range of 108-109 Ωcm, and the correlation between the Te inclusions and resistivity was investigated. The large size (>17 μm) and high concentration (4.5 of ×105 cm-3) Te inclusion decrease the resistivity of the CMT crystal seriously.

Microstructure and Electrical Characterization of In-Doped Cd0.9Mn0.1Te Crystal Grown by the Vertical Bridgman Method

CdMnTe is one of the key materials for room temperature X-ray and gamma-ray detectors on Environmental Analysis and Monitoring. In this paper, the homogeneous Cd1-xMnxTe (x = 0.1) single crystal ingot was grown by the vertical Bridgman method. The compositional analysis was carried out by SEM/EDS. The Te inclusions were revealed by the IR transmission spectra. In dopant distribution was determined by ICP-AES measurement. The resistivity of CdMnTe was cha-racterized by I-V method. It was found that the segregation coefficient of Mn was 0.97. In dopant contents within 3 to 21 ppm of the ingot were found. The Te inclusions were mainly 8.2-28.3m in size and 1×105-1.5×107cm-3in concentration. I–V measurement reveals that sputtered Au film can form good ohmic contact and all the slices have the resistivity within 107 to 109Ωcm.

Growth and Characterization of CdZnTe Bulk Crystals Grown by Temperature Gradient Solution Growth

CdZnTe bulk crystals were grown by temperature gradient solution growth (TGSG) method with the lower starting growth temperature of 1223K, temperature gradient of 20-30 K/cm and a crucible dropping rate varied from 1 to 0.6 mm/h. Optical microscope, IR microscope, I-V characteristics and FTIR transmission spectroscopy were employed to analyze the growth interfaces, Te inclusions, resistivity and IR transmittance respectively. The results indicate that a smooth and uniform growth interface has been achieved. The density of Te inclusions is about 7.9-9.5×103 cm-2, while the resistivity is higher than 6.87×109 Ωcm and the IR transmittance is about 55-60%.

Characterization of Indium-Doped CdZnTe Crystal Grown under Te-Rich Conditions

CdZnTe (CZT) crystals with a diameter of 52 mm was grown using low pressure Bridgman method and were indium-doped under Te-rich conditions. Results showed the Te concentration was almost the same in different part of the as-grown ingot. Through IR transmission, Te inclusion with regular triangular or circular shapes could be observed, and the size of Te inclusion was around 7 µm and the concentration was 1.5  105 cm-3 for the CZT in the middle part of the ingot. I-V characteristic showed a good linear behavior with a resistivity of ~1010 Ω•cm.

Preparation and Properties of N-ZnS Film/P-Si Heterojunction

ZnS films were prepared on silicon (Si) and glass substrates by radio-frequency (RF) magnetron sputtering method. The effect of annealing treatment on the structural and optical properties of ZnS films was studied. The results showed that annealing treatment was helpful in improving the crystalline quality of the ZnS films, and the bandgap was about 3.61eV and 3.49eV for films with and without annealing, respectively. A ZnS/ Si heterojunction diode was fabricated successfully by depositing ZnS films on p-type single-crystalline Si substrates. The electrical and optical property of the device was reported.

ZnO Films Deposited on Various Diamond Film Substrates with Different Surface Roughness

ZnO thin films were deposited by radio frequency (R. F.) magnetron sputtering on various diamond film substrates with different surface roughness. The influence of surface roughness on structural properties and surface morphology of ZnO thin films was investigated by X-ray diffraction (XRD) and atom force microscopy (AFM), respectively. Only on the nanocrystalline and free-standing diamond substrates, ZnO films with preferential c-axis orientation and smooth surface were obtained.

Effects of Annealing Treatment and Buffer Layer on Properties of ZnMgO Films Prepared on Diamond Substrates

ZnMgO films were prepared at room temperature on freestanding diamond (FSD) substrates with and without ZnO buffer layers by radio-frequency (RF) reactive magnetron sputtering method. The effects of annealing treatment and ZnO buffer layers on the structural, optical, and electrical properties of the ZnMgO films were studied by X-ray diffraction (XRD), UV-visible spectrophotometer, and electrical measurements. The experimental results suggested that the annealing treatment and buffer layer were helpful to improve the crystalline quality of ZnMgO/diamond heteroepitaxial films.