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We investigated the photoluminescence (PL) of CdTe doped with indium using above- and below-bandgap excitation at temperatures of 4.5-20 K. We recorded and measured the selectively excited PL arising from the recombination of donor-acceptor (D-A) pairs with the A-center acceptor in the spectral region of the 1.4-eV PL band for different excitation photon energies, hωEXC. Sharp, strong PL lines that shifted with hωEXC over the total contour of the D-A pair band represented the selective pair luminescence (SPL). The energy difference of ∼125 meV between the excited- and ground-state of the charged D-A pair is very close to the 6-longitudinal-optical phonon energy in CdTe. This multiplicity favors the relaxation of an excited hole to the ground state of an acceptor, and increases the probability of recombination in the D-A pair. The SPL line quenches with temperature, characteristically with energy of 6-14 meV for D-A pairs with different D-A distances. The temperature shift of the 1.4-eV band supposedly is caused by the redistribution of occupied- and empty-shallow donors neighboring the A-center. [ABSTRACT FROM AUTHOR]

Using photoluminescence (PL) and current deep-level transient spectroscopy (I-DLTS), we investigated the electronic defects of indium-doped detector-grade CdMnTe:In (CMT:In) crystals grown by the vertical Bridgman method. We similarly analyzed CdZnTe:In (CZT:In) and undoped CdMnTe (CMT) crystals grown under the amount of same level of excess Te and/or indium doping level to detail the fundamental properties of the electronic defect structure more readily. Extended defects, existing in all the samples, were revealed by synchrotron white beam x-ray diffraction topography and scanning electron microscopy. The electronic structure of CMT is very similar to that of CZT, with shallow traps, A-centers, Cd vacancies, deep levels, and Te antisites. The 1.1-eV deep level, revealed by PL in earlier studies of CZT and CdTe, were attributed to dislocation-induced defects. In our I-DLTS measurements, the 1.1-eV traps showed different activation energies with applied bias voltage and an exponential dependence on the trap-filling time, which are typical characteristics of dislocation-induced defects. We propose a new defect-trap model for indium-doped CMT crystals. [ABSTRACT FROM AUTHOR]

Focuses on a study which characterized iodide crystals with semitransparent metal overlayers of indium and tin using low-temperature photoluminescence spectroscopy. Discussion of the interaction between mercuric iodide and semitransparent metal overlayers; Application of photoluminescence spectroscopy; Observation on the behavior of photodetectors and indium-tin-oxide.

Deals with a study of mercuric-iodide photodetectors with sputtered indium-tin-oxide entrance electrodes using low-temperature photoluminescence spectroscopy. Experimental details; Results and discussion; Conclusion.

Focuses on a study which measured low-temperature photoluminescence spectra of detector grade direct-band-gap ternary compound to obtained information about shallow level defect concentration during mechanical polishing and chemical etching processes. Information on the ternary compound; Methodology of the study; Results and discussion.

Presents a study which introduced extrinsic defects into mercuric iodide during processing using low temperature photoluminescence spectroscopy measurements. Experimental technique; Results of the study; Conclusion.

Investigates the semitransparent palladium contacts on mercuric iodide. Use of the photoluminescence spectroscopy process; Modifications in the stoichiometry within the palladium/mercuric iodide interfacial region; Significance of dominant traps in the application of nuclear detection.

Presents a study which investigated the near-band-gap 4.2 K photoluminescence spectrum of undoped mercuric iodide in its red tetragonal form. Experimental techniques used; Results and discussion.

Presents information on a study which characterized the low-temperature photoluminescence spectra of several mercuric iodide detectors and off-stoichiometric bulk material. Experimental method; Raman measurements; Description of the photoluminescence spectra; Examination of the near-band-gap photoluminescence.

One of the most fundamental parameters relating to bulk crystal growth of CZT from the melt is the temperature gradient applied at the solid-liquid interface throughout the growth cycle. Cd1-xZn_xTe ingots grown by the vertical gradient freeze method, using dynamic temperature gradients are presented. Several complementary experimental methods have been implemented to investigate the material including mapping of resistivity, photosensitivity, infrared transmission, and measuring the low-temperature photoluminescence. Photoconductivity mapping was performed by the contactless method. Correlation of contactless resistivity and photoconductivity maps illustrate that both parameters are anticorrelated in the middle of the ingots, but correlated towards the tail end of the ingot. This observation is explained in terms of an energy shift of the Fermi level that changes the average occupation of a mid-gap level. This reasoning is further supported by photoluminescence data. [ABSTRACT FROM AUTHOR]

We report a substantial reduction in the impurity concentration of semi-insulating CdTe:Ge grown by the vertical Bridgman method by using sublimation of the feed material. Specific resistivity (ρdark) values of up to 3 x 109 Ω cm were obtained for samples with a relatively high photosensitivity (PS) value and optimal compensation. Concentrations of impurities in the feed and as-grown crystals were determined by the glow discharge mass spectroscopy (GDMS) method. The energy levels in the band-gap were studied by photoluminescence (PL), and the data were correlated with the GDMS measurements. The highest values of ρdark and PS were observed in the regions where the PL bands via the deep levels of Ge and Te antisite were present. [ABSTRACT FROM AUTHOR]

We utilized a low-temperature spatially resolved micro-photoluminescence mapping technique to investigate the spatial variation of photoluminescence- and electronic-defect states in areas of CdZnTe (CZT) single crystals containing structural-imperfections. Photoluminescence mapping of the donor-bound-exciton emission reveals an unexpected blue-shift of the CZT bandgap at Te inclusions, which indicates that for optical measurements the localized strain field needs to be considered for accurate calculation of Zn composition and energy levels near micro-scale defects. We observed that the line widths of the donor-bound-exciton peak and defect-related D band are broadened in regions with a high density of dislocations; in contrast, the donor-acceptor-pair peak is narrowed. [ABSTRACT FROM AUTHOR]

We report on the recharging of the neutral state of a deep-donor layer that increases the efficiency of charge collection in detector-grade CdTe:In. Measurements with photoinduced current transient spectroscopy and thermoelectric effect spectroscopy revealed positively charged energy level at EC-0.65 eV. Photoluminescence measurements identified this level being responsible for the 0.68 eV emission band. Its positive charge is converted into a neutral one by the upward displacement of Fermi level. We discuss the nature of this deep defect based on the latest ab initio calculations. [ABSTRACT FROM AUTHOR]

Specimens of mercuric iodide with evaporated semitransparent palladium contacts have been studied using low-temperature photoluminescence spectroscopy. Distinct differences were found between spectra taken from beneath the Pd contacts and those taken from regions on the HgI2 sample that were masked during the Pd deposition, indicating that contact fabrication can change the defect structure near the contact/substrate interface. Comparison of the spectra from spots beneath the contacts with spectra from bulk material specimens and HgI2 detectors graded in terms of their nuclear detection performance suggests that the processing steps used to deposit electrical contacts and the choice of contact material may have a significant influence on detector performance. [ABSTRACT FROM AUTHOR]

We studied the resistivity, photosensitivity, photoluminescence, and surface photovoltage of CdTe crystals doped with Ge or Sn to extend our knowledge of the influence of the deep-donor level on compensation and afterglow effects. We demonstrated a strong correlation between photosensitivity caused by photoelectrons with Fermi-level variations near the GeCd0/2+ or SnCd0/2+ energy levels. Surface photovoltage measurements confirmed that when the concentration of residual acceptors varied along the direction of growth, then trapping conditions dramatically changed as a defect was converted from a neutral state to doubly charged positive one. [ABSTRACT FROM AUTHOR]

Cd1-xZnxTe (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 (μτ) h of the CZT detector measured by DC photoconductivity is 7.0 x 10-4cm²/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 γ-rays, respectively. We have clearly shown the equivalence of charge collection efficiency results measured by both DC photocurrent and a particle response. Low-temperature 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 (D0, X) or neutral acceptors (A0, X), depending on the temperature, concentration of donors and acceptors, and the incident light intensity. It was found that the luminescence of (D0, X) depends linearly on the incident laser intensity, while (A0, X) has a nonlinear dependence. [ABSTRACT FROM AUTHOR]