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Growth of SiC from Si melt
Vol. 2, No. 6
ABSTRACTS OP PAPERS IN SOVIET PHYSICS-SOLU STATE
When CdTe is excited by fast electrons, radiative recombination occurs spectrum, in the photon energy range of 0. whose 7 to 1.6 eV, consists of three intense lines peaking at 1.05 * 0.01, 1.47 * 0.01 and 1. 59 ±0.01 eV at 10°K. We studied the temperature dependence of intensity and energy of the radiative recoinbination in the temperature range of 10-300°Kwith pulsed excitation by a beam of fast electrons. An electrostatic generator produced pulses of 1 MeV electrons at 1 to 20 cps repetition rates and of 1 to 100 ~sec duration. The rise time and decay of the pulses did not exceed 0. 15 .isec. The pulse current was about 3 ma. The sample thickness did not exceed 0. 5 mm, which is approximately a typical ionization depth for 1 MeV electrons in CdTe. The current density of fast electrons at the sample was close to 0. 5 ma/cm2 during the pulse. The spectral distribution of the recombination light was obtained with a glass prism spectrometer having a resolution of 0.07 eV/mm in the spectral range studied. A FEU-28 photomultiplier was the detector for photons above 1. 1 eV, and a germanium photodiode FD-1 was used for the range 0. 7-1.2 eV. The spectrum was recorded on a EPP-09 recorder. The received signal was amplified by a broad-band amplifier (USh-2) and fed to a pulse millivoltmeter (MW-i) which integrated the pulsed signal from the recombination light. It is shown that the short wavelength emission line lies within thr range of the Intrinsic absorption band and h~sa temperature coefficient of (4.0 * 0. 1) eV/degree. At 10°K, the short wavelength emission line exhibits a structure in the form of two steps which, from the authorsT point of view, can be explained as radiative transitions with the emisslon of longitudinal optical phonons having an energy of 0.020 * 0.002 eV. There is a discusslon of the nature of radiative recombinatlon in CdTe when it is excited by fast electrons and of the possibility of amplifying the radiation, X
10
Bibliography: 10 titles. GROWTH OF SIC FROM SI MELT. Yu. M. Shashkov and N. Ya. Shushlebina (Vol. 6, No. 5, pp. 1449-1452). This Is a study of the growth of single crystals of B-SiC from SI solution. A resistanceheated vacuum furnace was used similar to furnaces used for pulling single crystals of silicon. The furnace had a tantalum heater and permitted lowering and rotating the crucible and
iii
also lowering and lifti~iga probe. The melt was mm Hg. The In a vacuum of the ord~rof i04 crucible. silicon was melted in graphite Single crystal Si with a specific resistivity of 10-20 ohm-cm was used. T~ietemperature was controlled by a thermocot4ple at the bottom of the crucible. The instant of melting was determined visually. A second th~rmocouplewas used to determine the tempe$ture gradient in the melt by lowering it into the melt for the measurement and withdrawing it after the measurement.
a
Four types of Sic single-crystals were found forming in the S~melt. Their photographs are shown. Those moat characteristic of the majority of single-cry~talswere chosen for a study of the facets. Their schematic aspect is shown, and the result~of goniometric measurements are reported fo~each type of crystal. Measurements show tt~atthe (111) plane is the main facet (according ~oarea). In addition to (111) facets one finds ~100), (221) and (115) facets. -
Bibliography: 2 titles. V-I CHARACTERIS]~ICSOF p-n JUNCTIONS IN HEAVILY DOPED (iaAs. B. M. Vul, E. I. Zavaritskaya and A. P. Shotov (Vol. 6, No. 5, pp. 1465-1471). The V-I charactfristics of p-n junctions were studied in GaAs *ith tellurium c 17 and 1018 cm9centrafor tions T = 4.2 of and the order 77°K.ofTh~ iQ samples studied were the same as those prepared for the study of luminescence frojn pnjunctions. The pn junction area was S ~ 10° cmh~. The area of the heattransferring surface (S = 2 cm2) established thermal contact between the specimen and the liquid during power diSsipations of up to 1 watt. Results of measureme~itsof forward and reverse V-I characteristics ~ reported for one of the samples with a— 1010 ~m-3 tellurium concentration. The results of n~easurementson various samples vary little fro~nsample to sample for currents I >10-4 A. A~lower currents, they are considerably different, which Is apparently tied to side effects, whose ~mportance decreases as the current increases *nd becomes negligible at I,~i0’3A. Itwasest4bllshedthatbreakdown was observed In the di~placementof reverse characteristics, and Ir~all samples a smooth rise in current was ob5erved with Increasing voltage. It is shown fi4rther th~when the tellurium concentratioi~is 10~~ cm3 the dependence of the curr~nton the voltage across the pn junction coincides with the dependence of —
ABSTRACTS OP PAPERS IN SOVIET PHYSICS-SOLU STATE
When CdTe is excited by fast electrons, radiative recombination occurs spectrum, in the photon energy range of 0. whose 7 to 1.6 eV, consists of three intense lines peaking at 1.05 * 0.01, 1.47 * 0.01 and 1. 59 ±0.01 eV at 10°K. We studied the temperature dependence of intensity and energy of the radiative recoinbination in the temperature range of 10-300°Kwith pulsed excitation by a beam of fast electrons. An electrostatic generator produced pulses of 1 MeV electrons at 1 to 20 cps repetition rates and of 1 to 100 ~sec duration. The rise time and decay of the pulses did not exceed 0. 15 .isec. The pulse current was about 3 ma. The sample thickness did not exceed 0. 5 mm, which is approximately a typical ionization depth for 1 MeV electrons in CdTe. The current density of fast electrons at the sample was close to 0. 5 ma/cm2 during the pulse. The spectral distribution of the recombination light was obtained with a glass prism spectrometer having a resolution of 0.07 eV/mm in the spectral range studied. A FEU-28 photomultiplier was the detector for photons above 1. 1 eV, and a germanium photodiode FD-1 was used for the range 0. 7-1.2 eV. The spectrum was recorded on a EPP-09 recorder. The received signal was amplified by a broad-band amplifier (USh-2) and fed to a pulse millivoltmeter (MW-i) which integrated the pulsed signal from the recombination light. It is shown that the short wavelength emission line lies within thr range of the Intrinsic absorption band and h~sa temperature coefficient of (4.0 * 0. 1) eV/degree. At 10°K, the short wavelength emission line exhibits a structure in the form of two steps which, from the authorsT point of view, can be explained as radiative transitions with the emisslon of longitudinal optical phonons having an energy of 0.020 * 0.002 eV. There is a discusslon of the nature of radiative recombinatlon in CdTe when it is excited by fast electrons and of the possibility of amplifying the radiation, X
10
Bibliography: 10 titles. GROWTH OF SIC FROM SI MELT. Yu. M. Shashkov and N. Ya. Shushlebina (Vol. 6, No. 5, pp. 1449-1452). This Is a study of the growth of single crystals of B-SiC from SI solution. A resistanceheated vacuum furnace was used similar to furnaces used for pulling single crystals of silicon. The furnace had a tantalum heater and permitted lowering and rotating the crucible and
iii
also lowering and lifti~iga probe. The melt was mm Hg. The In a vacuum of the ord~rof i04 crucible. silicon was melted in graphite Single crystal Si with a specific resistivity of 10-20 ohm-cm was used. T~ietemperature was controlled by a thermocot4ple at the bottom of the crucible. The instant of melting was determined visually. A second th~rmocouplewas used to determine the tempe$ture gradient in the melt by lowering it into the melt for the measurement and withdrawing it after the measurement.
a
Four types of Sic single-crystals were found forming in the S~melt. Their photographs are shown. Those moat characteristic of the majority of single-cry~talswere chosen for a study of the facets. Their schematic aspect is shown, and the result~of goniometric measurements are reported fo~each type of crystal. Measurements show tt~atthe (111) plane is the main facet (according ~oarea). In addition to (111) facets one finds ~100), (221) and (115) facets. -
Bibliography: 2 titles. V-I CHARACTERIS]~ICSOF p-n JUNCTIONS IN HEAVILY DOPED (iaAs. B. M. Vul, E. I. Zavaritskaya and A. P. Shotov (Vol. 6, No. 5, pp. 1465-1471). The V-I charactfristics of p-n junctions were studied in GaAs *ith tellurium c 17 and 1018 cm9centrafor tions T = 4.2 of and the order 77°K.ofTh~ iQ samples studied were the same as those prepared for the study of luminescence frojn pnjunctions. The pn junction area was S ~ 10° cmh~. The area of the heattransferring surface (S = 2 cm2) established thermal contact between the specimen and the liquid during power diSsipations of up to 1 watt. Results of measureme~itsof forward and reverse V-I characteristics ~ reported for one of the samples with a— 1010 ~m-3 tellurium concentration. The results of n~easurementson various samples vary little fro~nsample to sample for currents I >10-4 A. A~lower currents, they are considerably different, which Is apparently tied to side effects, whose ~mportance decreases as the current increases *nd becomes negligible at I,~i0’3A. Itwasest4bllshedthatbreakdown was observed In the di~placementof reverse characteristics, and Ir~all samples a smooth rise in current was ob5erved with Increasing voltage. It is shown fi4rther th~when the tellurium concentratioi~is 10~~ cm3 the dependence of the curr~nton the voltage across the pn junction coincides with the dependence of —