Characterization of Cd1−xZnxTe crystals grown from a modified vertical bridgman technique

Abstract

Cd 1ÿ x Zn x Te (CZT) crystals grown from a modified vertical Bridgman technique were characterized by means of an optical polarized transmission technique using the Pockels effect, low-temperature direct current (DC) photoconductivity technique, low-temperature photoluminescence (PL) spectroscopy, room-temperature PL mapping technique, and detector performance measurements. Electric field mapping indicates that an approximation of a uniform electric field distribution approximation is generally satisfied for CZT detectors operated at room temperature under typical working conditions. A nonuniform electric field distribution is observed under intense infrared (IR) light illumination, and a model is proposed based on charge generation of defects, trapping, and space-charge effects. The largest hole mobility-lifetime product (mt) h of the CZT detector measured by DC photoconductivity is 7.0 3 10 ÿ 4 cm 2 /V. The detector treated with 2% bromine in methanol chemical etch has a relatively small surface recombination velocity at room temperature, which was obtained from DC photocurrent and detector performance tests, as measured by irradiation of 5.5-MeV a particles and 59.6-keV g-rays, respectively. We have clearly shown the equivalence of charge collection efficiency results measured by both DC photocurrent and a particle response. Lowtemperature DC photocurrent measurements show that surface recombination velocity increases significantly with decreasing temperature from 300 K to 250 K. The effective electron mobility-lifetime product-combination effects of bulk and surface of CZT crystal-increases with increment of temperature. Room-temperature PL mapping measurements indicate uniformity of zinc concentration within CZT crystals. Low-temperature PL spectroscopy shows that the dominant emission peaks are excitons, which are bound to either shallow neutral donors (D 0 , X) or neutral acceptors (A 0 , X), depending on the temperature, concentration of donors and acceptors, and the incident light intensity. It was found that the luminescence of (D 0 , X) depends linearly on the incident laser intensity, while (A 0 , X) has a nonlinear dependence.

Study of Te inclusions in CdMnTe crystals for nuclear detector applications

“…In this work, we studied CdMnTe crystals grown by modified low-pressure Bridgman (MLPB) technique at Yinnel Tech [13]. Infrared (IR) microscopy was used to screen the crystals for the presence of defects, specifically twins and Te inclusions.…”

Growth of spectroscopic grade Cd0.9Zn0.1Te:In by THM technique

“…The above (mt) e values extracted with different sources are in reasonably good agreement with each other. The shaping time for 5.5 MeV source was 4 ms, while for all g sources the shaping used was 1 ms. Y. Cui et al [18] also reported similar (mt) e values obtained with different excitations like photo current, alpha source, and 59.6 and 662 keV gamma sources. The (mt) e value obtained from other samples from the same ingot were in the range 4-7 Â 10 À 3 cm 2 /V.…”

Property Improvement in CZT via Modeling and Processing Innovations . Te-particles in vertical gradient freeze CZT: Size and Spatial Distributions and Constitutional Supercooling

“…The need for high-purity cadmium-zinc-telluride (CZT) crystals for high-resolution radiation detection is well documented and many research groups are engaged in crystal growth of CZT [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16], in fabrication of gamma-ray detectors from CZT [15,[17][18][19][20][21][22][23], and in the design of detector systems based on CZT [18,[24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. A ubiquitous problem for CZT crystals is the unwanted incorporation of Te-particles or Teprecipitates within the CZT crystal during the crystal growth process, in addition to other crystal defects.…”