The effects of two intrinsic deep levels on electrical compensation in semi-insulating CdTe and Cd-Zn-Te crystals are reported here. These levels were found in samples grown by conventional Bridgman and highpressure Bridgman techniques. The levels were observed with thermoelectric effect spectroscopy at distinct temperatures corresponding to thermal ionization energies of E d1 ϭE v ϩ0.735Ϯ0.005 eV and E d2 ϭE v ϩ0.743Ϯ0.005 eV. The first level is associated with the doubly ionized Cd vacancy acceptor and the second level was tentatively identified as the Te antisite (Te Cd ), which is thought to be complexed with a vacancy. The second level was found to electrically compensate CdTe and Cd-Zn-Te to produce high resistivity crystals, provided that the Cd vacancy concentration is sufficiently reduced during crystal growth or by post-growth thermal processing.The relatively wide band gap, large atomic numbers, and good carrier mobility render CdTe and Cd-Zn-Te ͑Refs. 1 and 2͒ as promising materials for room-temperature radiation sensor applications. High resistivity is necessary but not sufficient for production of CdTe and Cd-Zn-Te radiation detectors. To realize the maximum resistivity of CdTe and CdZn-Te crystals allowed by the band gap a net carrier concentration of 10 8 cm Ϫ3 or lower has to be achieved. Early attempts to produce high resistivity CdTe and Cd-Zn-Te crystals by common growth techniques resulted in materials with native defect or impurity concentrations on the order of 10 15 cm Ϫ3 and carrier concentrations orders of magnitude in excess of the requirements for intrinsic resistivity. Recently, high resistivity CdTe and Cd-Zn-Te crystals have been grown with both high-pressure Bridgman 3 ͑HPB͒ 4 and vertical Bridgman with overpressure control ͑VBOC͒ techniques. In this paper we show that intrinsic defects compensate CdTe and Cd-Zn-Te resulting in semi-insulating materials in spite of a total impurity concentration of ϳ10 15 cm Ϫ3 , which is achievable with current technologies.Samples of CdTe and Cd-Zn-Te were characterized with current-voltage measurements (I-V), glow discharge mass spectroscopy ͑GDMS͒, and thermoelectric effect spectroscopy ͑TEES͒. 5 The electrical transport properties of the samples including bulk electrical resistivity were studied by I-V measurements. The thermal activation energies of the various defect levels were extracted from TEES data. Results on four different representative CdTe and Cd-Zn-Te crystals are presented in this paper. The samples were grown by eV PRODUCTS using the HPB technique and by Johnson Matthey Electronics ͑JME, now Honeywell Electronic Materials͒ using the VBOC technique. The eV samples included Cd 0.9 Zn 0.1 Te and CdTe samples, as well as an Al-doped CdTe sample. 6 The JME samples were all Cd 0.85 Zn 0.15 Te. The total residual impurity concentration was on the order of 10 15 cm Ϫ3 for all samples studied. Glow-discharge mass spectroscopy ͑GDMS͒ data for selected elements, which are discussed in the literature as candidates for midgap trap, are shown...
Epitaxial films of barium hexaferrite (BaFe12 O19 ) have been prepared on basal-oriented sapphire substrates by rf sputter deposition of an amorphous ferrite film and crystallization of the film by annealing. Liquid phase epitaxy has been used to deposit an additional barium hexaferrite layer on top of the sputter deposited and annealed film. In this way films having symmetric ferromagnetic resonance peaks as narrow as 41 Oe at 60 GHz have been obtained.
Crystalline properties of Si-implanted 〈100〉 GaAs, Si, and Ge have been studied by Bragg case double-crystal x-ray diffraction. Sharp qualitative and quantitative differences were found between the damage in GaAs on one hand and Si and Ge on the other. In Si and Ge the number of defects and the strain increase linearly with dose up to the amorphous threshold. In GaAs the increase in these quantities is neither linear nor monotonic with dose. At a moderate damage level the GaAs crystal undergoes a transition from elastic to plastic behavior. This transition is accompanied by the creation of extended defects, which are not detected in Si or Ge.
For microwave and millimeter-wave applications, there is increasing interest in using ferrite films rather than bulk ferrites. In some cases, such as magnetostatic wave devices, films provide definite performance advantages. In other cases, films may provide lower cost, smaller size, and enhanced compatibility with planar circuit designs such as monolithic microwave integrated circuits (MMlC). The relatively limited research on ferrite films for microwave and millimeter-wave applications has borrowed from the more extensive work that has been motivated by applications to various forms of magnetic recording. An example is the YlG (yttrium iron garnet) epitaxial film, brought to a high level of development as a by-product of bubble memory technology and now coming into use for tunable microwave filters and for magnetostatic wave devices. Similarly, other magnetic recording materials point the way to development of ferrite films suitable for other microwave and millimeter-wave applications including, eventually, fully monolithic incorporation into MMlC technology.
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