Behavior of copper in gallium arsenide with high tin concentration

Investigations were made of the electrical properties, the cathodolumiescence and photoconductivity spectra, and the temperature dependence of the majority carrier lifetime in gallium arsenide with a high concentration of tin (n=2·10¹⁸ cm^–3, 1.5·10¹⁷ cm^–3) that was doped with copper under different diffusion regimes. Measurements of the Hall effect revealed centers with an ionization energy 0.175 ± 0.005 eV, their concentration depending on the rate of cooling of the samples. The cathodoluminescence and Hall effect data suggest that the cathodoluminescence band observed at 1.35 eV in GaAsSnCu is associated with radiative transitions of electrons to centers with _a =E_v + 0.175 eV. The hole lifetime in GaAsSnCu has a complicated temperature dependence which can be explained qualitatively by the presence of two types of capture center.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 58–63, September, 1980.     

Diffusion of Al in ion-implanted α-Zr and α-Hf

The diffusion of Al in the group IVa metals Zr and Hf has been studied for the first time in the temperature ranges 600°–800°C (Zr) and 750°–900°C (Hf) using ion-beam techniques. Diffusion couples were created by ion-implantation. The time-dependent diffusion profiles were monitored by the use of the Nuclear Resonance Broadening (NRB) technique. The linear Arrhenius plots extracted from the measured diffusivities indicate that the diffusivity of implanted Al in Zr and Hf can be described by the activation energyQ=2.9±0.2eV and 3.7±0.3eV and the pre-exponential factorD ₀=17±42cm²/s and 170±600cm²/s, respectively.     

Annealing behaviour of C-implanted α-Hf

The annealing behaviour of C in the group IVa metal Hf has been studied in the previously uninvestigated temperature range 650–800°C using ion-beam techniques. Diffusion couples were created by ion implantation. The time evolution of the carbon profiles were monitored by the use of the Nuclear Resonance Broadening (NRB) technique. The linear Arrhenius plot extracted from the measurements indicates that the diffusivity of implanted C in polycrystalline h.c.p. -Hf can be described by the activation energyQ=3.9±0.2 eV and the pre-exponential factor D₀=(50± ₄₇ ¹²⁰ )×10⁵ cm²/s. The implanted distributions were used to determine the solubility of C in -Hf for the first time.     

Annealing behavior ot trap-centers in silicon containing A-swirl defects

The annealing behavior of trap-centers was studied in float-zone silicon wafers containing A-swirl defects. Samples from areas of high and low A-swirl density were annealed in nitrogen ambient between 100° and 900 °C, and analysed using the Deep Level Transient Spectroscopy. The results indicate, that two levels atE _c }-0.07 eV, _n=4.6×10^–16 cm², andE _c–0.49eV, _n=6.6×10^–16cm² are caused by one defect, for which the silicon di-selfinterstitial is a likely interpretation. A level atE _c }-0.11 eV was assigned to interstitial carbon. Both defects annealed out at about 170 °C. After 600 °C annealing an additional level atE _c–0.2 eV was detected, which was attributed to an interstitial silicon carbon complex. Heat treatment at 800 °C generated a new level atE _c–0.49 eV, _n=2.9×10^–16cm² only in the area of high A-swirl defect density. This level was also observed after oxidation and subsequent annealing of silicon.     

Forbidden lines in the hyperfine spectrum of the electron paramagnetic resonance of Mn++ in BaTiO3

The hyperfine spectrum of Mn⁺⁺ in powder BaTiO₃ was studied at 8740 MHz andT=80°K. The measured lines appearing as doublets between the hyperfine lines of Mn⁺⁺ are explained as forbidden transitions of the typeM=±1,m=±1. A theoretical expression for the position of these doublets is given and some of the constants of the spin Hamiltonian are determined:g=2.001±0.001, ¦A¦=86 Oe,D 40 Oe.     

Excited donor and acceptor states in zinc telluride

Excited shallow donor and acceptor states are observed in excitation spectra of donoracceptor pair luminescence in ZnTe. The experiments yield a donor ionization energyE _D =18.3±0.3 meV, and from the Li acceptor 2P _3/2, 2P _5/2( ₈), and 2P _5/2( ₇) states valence band parametersµ=0.60±0.10 and=0.22±0.05. The latter exceeds values derived from other experiments and indicates considerable nonspherical perturbations associated with this acceptor requiring an extension of existing theories for shallow acceptor states.     

Decay of Re186

The decay of Re 186 was investigated with a double focusing spectrometer and scintillation spectrometer. Four transitions were observed with energies of 122·7±0·1 keV, 137·2 keV, 632·2±1·5 keV and 768·2±1·5 keV and the relative-ray intensities 18, 246, 0·9 and 1 respectively. TheK-conversion coefficients determined for low-energy transitions are in good agreement with the theoretical values ( _K ^122·7 =0·53±0·05, _K ^137·2 =0·44±0·02). The relative intensities of theK, L, M andN conversion lines were also determined for these transitions:KL _I +IIL _III M=1·20±0·201·32±0·20 1±0·150·57±0·08 for 122·7 keV transition,KL _I +IIL _III MN=1·57±0·081· 72±0080·70±0·030·20±0·01 for 137·2 keV transition. In the beta spectrum two groups were observed with the end points of 1076±3 keV and 939±3 keV and relative intensities 74±4% and 21±4% respectively. For the branching ofK-capture it was found that 1·5% populates the 122·7 keV level and 3·5% the ground state. The decay scheme from the present results is proposed.The authors would like to thank M. Buriánek and V. Kopiva for help in the measurements.     

Decay of Cs134m

The decay of the isomeric state of Cs¹³⁴ was studied. The decay half-timeT _1/2=2·93±0·05 hours was determined. From measurements carried out by means of a spectrometer with short lens, scintillation measurements and chemical separations, the non-existence of the weak decay of this state was proved, contrary to statements found previously in the literature (maximum possible intensity 0·02%, compared to the value of 1% found in the literature). The spectrum of conversion electrons was measured by a double-focusing spectrometer, and the following transition energies were determined: 127·3±0·3 keV (E3) and 138·4±0·4 keV (M4) (K:L:M+N is 92 100 27 for the 127·3 keV transition, and 206 100 31 for the 138·4 keV transition). The conversion coefficient of the 127 keV transition was measured, resulting in a value of _k =2·55±±0·4. The ratio of transition intensities isI ₁₃₈ I ₁₂₇=5·7 1000.     

Measurement of the2H(d, γ)4He reaction at intermediate excitation energies

The²H(d, )⁴He differential cross section was measured at deuteron laboratory energies of 20, 24, and 28 MeV between _cm=45° and _cm=135°. AtE _d =28 MeV a complete angular distribution was determined and fitted with Legendre polynomials. The ratioR=d/d (_cm=90°)/d/d (_cm=135°) was measured for each deuteron energy.     

X-rays from antiprotonic3He and4He

Antiprotonic X-rays from the helium isotopes have been observed at pressures of 36, 72, 375 and 600 mbar. The antiproton beam from LEAR with momenta of 309 and 202 MeV/c has been stopped at these pressures using the cyclotron trap. The X-rays were detected with Si (Li) and intrinsic Ge semiconductor detectors. Absolute X-ray yields were determined and the strong-interaction 2p shifts and the 2p and 3d broadenings measured to be _2p=(–17±4) eV, _2p=(25±9) eV and _3d=(2.14 ±0.18) meV for ¯p³He and _2p=(-18±2) eV, _2p =(45±5) eV and _3d=(2.36±0.10) meV for ¯p⁴He.The efforts of the LEAR staff and the help of P. Gauss from the CERN Cryogenic Group as well as the technical assistance of M. Dröge and M. Stoll are gratefully acknowledged. This work is part of the Ph.D. of one of us (M.S.), University of Karlsruhe (1987), KfK report no. 4222.     

Diffusion of nitrogen in ion-implanted chromium and tungsten

The diffusion of N in the group VI B metals Cr and W has been studied in the previously uninvestigated temperature ranges 300°–550 °C (Cr) and 600°–800 °C (W) using ion-beam techniques. Diffusion couples were created by ion-implantation. The timedependent diffusion profiles were monitored by the use of the Nuclear Resonance Broadening (NRB) technique. The linear Arrhenius plots extracted from the measured diffusivities indicate that the diffusivity of implanted N in Cr and W can be described by the activation energyQ=1.39±0.06 eV and 2.32±0.16 eV and the pre-exponential factorD ₀=(7.0±7.2)×10^–4cm^2/s and 4.3±8.3cm^2/s, respectively. The solubilities of N in Cr and W from the implanted distributions were found to deviate from those obtained using conventional metallographical methods.     

Energy gaps and phonon structures in tunneling spectra of Bi2Sr2Ca1Cu2O8+x and Bi2Sr2Ca2Cu3O10+y superconductors

Polycrystalline Bi-2212 or Bi-2223 systems and single crystals of the Bi-2212 system were investigated at several temperatures by means of the break-junction and point-contact tunneling techniques, respectively. In the case of Bi-2223 we obtained an averaged gap value 2=65±4 meV. The Bi-2212 system yields 2= 45±5 meV in the case of polycrystalline samples and 2=47±5 meV in the case of single crystals. Hence there result BCS-ratios 2/k _B T _c of 7.3, 6.8 and 6.5, respectively. A dc-Josephson-type supercurrent could be observed in polycrystalline Bi-2212 samples in addition to the usual gap structure. The point-contact tunneling spectra of Bi-2212 single crystals exhibit structures in the second derivative d² I/d V ² which we interpret as inelastic tunneling processes due to electron-phonon scattering most likely in the barrier region. The phonon energies deduced from these structures are in accordance with data obtained from inelastic neutron scattering and Raman spectroscopy. Good agreement is obtained with a lattice dynamical calculation of the partial phonon densities of states of individual atoms in the unit cell.     

Solubility of Na2Co3 in NaCl:CaCl2 crystals

Measurements of electrical conductivity of NaCl 10^–5 molar fr. CaCl2 (1–80)×10^–5 molar fr. Na₂CO₃ crystals have been used to determine the temperature dependence of the solubility of CO₃-ions over the temperature range from 75 to 530 °C. The total solubility of CO₃-ions and that of [CO ₃ ^2– -vacancy] complexes may be expressed by simple relationships andc _ka=3·19× 10^–2 exp (–0·25 eV/kT), resp. The heat of solution of complexes is equal to 0·25 eV and that of free CO ₃ ^2– ions is higher than 1·2 eV. Under conditions of the thermal equilibrium between the solid solution and precipitate, the ratio of Na₂CO₃ and CaCO₃ components in the precipitate has been calculated at various temperatures and CO₃ concentrations.     

The electronic structure of Rhodium: Angle-resolved studies of photoelectron and secondary electron emission

We report electron spectroscopic studies of the Rh(111) surface, with the aim to obtain bulk band-structure information. We have measured normal photoemision using tunable synchrotron radiation in the range of photon energies between 11 eV and 55 eV, and angle-dependent photoemission along the LUX and LKL azimuths using the He resonance lines (=21.2 eV, 40.8 eV). To complement these data, we studied angleresolved secondary electron emission after excitation with electrons and photons. We derive parts of the one-electron energy dispersionE(k) along L, and determine the energies of several bulk critical points (in eV):E(> ₇₊/₈₊)=–2.75±0.10,E(> ₈₊=–0.85±0.10,E(> _7–=16.1±0.5,E(> _6–/> _8–)=20.5±0.5,E(X ₇₊)=–5.0±0.1,E(L ₆₊)=–5.6±0.5,E(L ₆₊/L ₄₊₊₅₊)=–2.65±0.10,E(L ₆₊)=9.0±0.5 eV. Our results are compared to several available band structure calculations.     

Diffusion coefficient of selenium in indium antimonide

The diffusion of selenium in indium antimonide has been studied in the temperature range 400–490°C, by the method of removing layers. Two regions have been distinguished in the donor distribution profiles. The first has a low diffusion coefficient and a high surface concentration, near to the limit of solubility of selenium (8·10¹⁸ cm^–3). In the second region, a much larger diffusion coefficient and a surface concentration lower by two orders of magnitude (8·10¹⁶ cm^–3) with weak temperature dependence are found. The temperature dependences of the diffusion coefficients of the first and second regions can be described by the expressions: D=4.8·10¹³ exp(–4.1 eV/kT) cm²/sec, D₂=1.9·10¹³ exp(–3.9 eV/kT) cm²/sec.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 40–43, November, 1991.     

Elasticp+12C scattering between 0.3 and 2 MeV

Absolute differential cross-sections ofp+¹²C elastic scattering have been measured at _cm=89.1°, 118.7°, 146.9° for bombarding energies between 0.3 and 2.0 MeV. Revised level parameters of the first three excited states in¹³N have been extracted with aR-matrix analysis. It is shown that the influence of the bound ground-state of¹³N has an appreciable effect on low-energy scattering. Recent predictions concerning Mott-Schwinger polarization are also discussed.     

Multi-exponential analysis of DLTS

Deep-level transient spectroscopy (DLTS), which is widely used to characterize deep impurity centers in semiconductors, assumes a single exponential wave form for the transient junction capacitance. When there are several closely spaced energy levels this assumption is no more valid, and the conventional DLTS may lead to errorneous results. To overcome this difficulty we propose here a novel method which we call the multi-exponential DLTS(MEDLTS). The transient wave form of the junction capacitance is directly analysed into multi-exponential compouents using the nonlinear least-squares analysis program DISCRETE developed by Provencher. The resolved time constants of these components are then displayed in the form of aT ²–1/T plot. According to the results of simulation with various parameters MEDLTS is shown quite effective to resolve closely spaced energy levels which can not be resolved by the conventional DLTS. As an example of the application of this method deep levels in Si: Au were investigated. The results have shown that a single peak in conventional DLTS actually consists of two adjacent levels with activation energies and capture cross-sectionsE _B1=0.49 eV, _B1=1.1×10^–14cm² andE _B2=0.46 eV, _B2=1.3×10^–15 cm² and with amplitude ratio 11.     

Determination of the strain potential constant by means of the p-InSb photoconductivity spectra under uniaxial compression

The influence of uniaxial pressure (0 < P < 2600 kg/cm2) on the intrinsic photoconductivity (PC) spectrum of p-InSb at 93 and 15°K is investigated. At 77°K the carrier concentration and mobility in the specimens were, respectively, (1.4–3.2)·10¹⁴ cm^–3 and 7000 cm²/V. sec. It is established that the maximum in the PC(E_m) spectra under compression is shifted towards higher energies. In the low-compression range E_m/P=5·10^–6eV·cm²/kg, while E_m/P=1·10^–6eV·cm²/kg for P > 1000 kg/cm². It is shown that the shift of the maximum of the intrinsic PC spectra with pressure is due to the growC;th in the forbidden bandwidth (E_g), and the change in parameters characterizing carrier diffusion in the specimen bulk (the diffusion coefficient, lifetime, surface recombination velocity) plays no part. The change in E_m/P with pressure is explained by the influence of valence band splitting. The deformation potential constants of the valence band |b|=(1.7±0.3) eV and |d|=(4.4±0.8)eV are calculated on the basis of a comparison between experimentally obtained data and theoretical results.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 159–162, February, 1976.     

The dependence of the neutron temperature on the geometric parameter for water and loose diphenyl

The dependence of the neutron temperatureT _n on the geometric parameterB ² was measured by the pulse method in water and loose diphenyl. The measurements were made on a moderator poisoned by cadmium sulphate, a substance whose absorption cross-section is non 1/v.The following results were obtained: For waterT _n [eV]=–(0·00391±0·00045)B ² [cm^–2]+(0·02537±0·00035) for loose diphenyl:T _n [eV]=–(0·01014±0·00152)B ² [cm^–2]+(0·02518±0·00054).We are indebted to J. Jirou and J. Jadavan for their assistance in the measurements, the accelerator operation and electronic apparatus maintenance.     

Interaction of excitons in indirect solid solutions of In1−xGaxP at high levels of excitation

The cathode luminescence spectra of GaP and solid solutions of In_1–xGa_xP (with an indirect energy band structure) obtained by liquid-phase epitaxy are investigated at T=77 and 9°K. It is established that the recombination of excitons on neutral donors and the pure exciton recombination with the participation of TA (=13±1 meV), LA (=31±1 meV), and TO (=43±2 meV) phonons. dominate in the low-temperature luminescence spectra of GaP and In_1–xGa_xP with a small concentration of photon impurities. The complex luminescence band that arises for sufficiently high levels of excitation and at T = 9°K is attributed to the luminescence of an electron-hole drop (EHD). The transformation of spectral form of the EHD band with the transition from GaP to In_1–xGa_xP is attributed to a simultaneous reduction in the contribution of the TA and TO replicas and to the appearance of a phononless component in the luminescence of the EHD.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 37–40, September, 1985.