Magnetic moment relaxation of a shallow acceptor center in heavily doped silicon

Results of studying the temperature dependence of the residual polarization of negative muons in crystalline silicon with germanium (9×10 ¹⁹ cm ^?3 ) and boron (4.1×10 ¹⁸ , 1.34×10 ¹⁹ , and 4.9×10 ¹⁹ cm ^?3 ) impurities are presented. It is found that, similarly to n-and p-type silicon samples with impurity concentrations up to ～10 ¹⁷ cm ^?3 , the relaxation rate ν of the magnetic moment of a _μ Al acceptor in silicon with a high impurity concentration of germanium (9×10 ¹⁹ cm ^?3 ) depends on temperature as ν～T ^q , q≈3 at T=(5–30) K. An increase in the absolute value of the relaxation rate and a weakening of its temperature dependence are observed in samples of degenerate silicon in the given temperature range. Based on the experimental data obtained, the conclusion is made that the spin-exchange scattering of free charge carriers makes a significant contribution to the magnetic moment relaxation of a shallow acceptor center in degenerate silicon at T?30 K. Estimates are obtained for the effective cross section of the spin-exchange scattering of holes (σ _h ) and electrons (σ _e ) from an Al acceptor center in Si: σ _h ～10^?13 cm² and σ _e ～8×10^?15 cm² at the acceptor (donor) impurity concentration n _a (n _d )～4×10¹⁸ cm^?3.     

Observation of raman scattering by localized optical phonons bound to neutral donors in GaP:Si

Raman scattering by localized optical phonons bound to neutral donors with degenerate ground state has been observed in GaP:Si. The scattering efficiency was measured at T=6.0±0.1 K as a function of the net donor concentration N_D-N_A ranging from 1.6 ·10¹⁷ to 7.1· 10¹⁷ cm^-3. It is found that reasonable agreement with the theory of weakly coupled electron-phonon modes obtained if a Bohr radius of $\text{a}{}_0\text{=5.4}\text{A}\text{?}$ is used, whereas $\text{a}{}_0\text{=7.5}\text{A}\text{?}$ is obtained in the hydrogenic effective-mass approximation using the ionization energy E_D=86.7 meV.     

Dependence of optically oriented and detected electron spin resonance on donor concentration in n-GaAs

Electron spin resonance of donors in GaAs has been observed through optical orientation and detection of spins. GaAs samples doped below the metal-insulator transition were studied. The resonance linewidth increases as the concentration of donors is reduced, due to the dependence of the T₂^* spin lifetime on correlation effects between donor electrons. The linewidth of the lowest doped sample (3×10¹⁴ cm⁻³) corresponds to a T₂^* of 5 ns, which is the value predicted for electrons in the non-interacting, localized limit. The nuclei need to be simultaneously depolarized in order to make the electron resonance observable.     

Exciton spectra and electrical conductivity of epitaxial silicon-doped GaN layers

Optical spectra and electrical conductivity of silicon-doped epitaxial gallium nitride layers with uncompensated donor concentrations N _D — N _A up to 4.8 × 10¹⁹ cm^?3 at T ≈ 5 K have been studied. As follows from the current-voltage characteristics, at a doping level of ～3 × 10¹⁸ cm^?3 an impurity band is formed and an increase of donor concentration by one more order of magnitude leads to the merging of the impurity band with the conduction band. The transformation of exciton reflection spectra suggests that the formation of the impurity band triggers effective exciton screening at low temperatures. In a sample with N _D — N _A = 3.4 × 10¹⁸ cm^?3, luminescence spectra are still produced by radiation of free and bound excitons. In a sample with N _D — N _A = 4.8 × 10¹⁹ cm^?3, Coulomb interaction is already completely suppressed, with the luminescence spectrum consisting of bands deriving from impurity-band-valence band and conduction-band-valence band radiative transitions.     

Spektroskopische Untersuchungen an DyAsO4

DyAsO₄ undergoes a crystallographic phase transition atT _D=11.2K which is induced by a cooperative Jahn-Teller-effect. As deduced from the optical absorption spectra the distance between the two lowest lying Kramers doublets of the Dy³⁺ ion is increased from (6.1±0.5) cm^?1 aboveT _D to (25.0±0.5) cm^?1 at 4.2 K. BelowT _D the splitting factor of the lowest doublet becomes nearly uniaxial with a maximum value ofg _b =17.5±1.0 along the crystallographicb-axis. AtT _N=2.44 K the crystals order antiferromagnetically. The absorption lines of Er³⁺ ions in DyAsO₄ show already a splitting immediately belowT _D which is explained by magnetic short range ordering of the Dy³⁺ ions in the temperature rangeT _{N D} .     

Photoluminescent studies of the condensed phase in phosphorus-doped silicon

Photoluminescent studies give evidence for the existence of the electron—hole droplet in phosphorus-doped silicon in the impurity concentration range 9.0 × 10¹⁵cm^?3 ? N_D ? 4.3 × 10¹⁹cm^?3.     

On the thermal conductivity of glasses

We estimate the numerical contribution of the interaction between like defects in glasses for the linewidth (? T^?1₂) obtained in acoustical experiments. This interaction gives origin to a diffusion process with a very large diffusion constant (D = 10^?5 cm² sec^?1). The thermal conductivity due to this diffusion process is calculated. Its temperature dependence is also obtained.     

Theoretical modelling of XBn T2SLs InAs/InAsSb/B-AlAsSb mid-wave detector operating below thermoelectrical cooling

The paper reports on the barrier mid-wave infrared InAs/InAsSb (x_Sb = 0.4) type-II superlattice detector operating below thermoelectrical cooling. AlAsSb with Sb composition, x_Sb = 0.97; barrier doping, N_D < 2×10¹⁶ cm^?3 leading to valence band offset below 100 meV in relation to the active layer doping, N_D = 5×10¹⁵ cm^?3 was proved to be proper material not introducing extra barrier in valence band in the analyzed temperature range in XBn architectures. The detectivity of the simulated structure was assessed at the level of ～ 10¹¹ Jones at T ～ 100 K assuming absorber thickness, d = 3 μm. The detector’s architecture for high frequency response operation, τ_s = 420 ps (T ～ 77 K) was presented with a reduced active layer of d = 1 μm.     

Influence of interchain coupling on the one-dimensional magnon raman spectrum of CsCoBr3

Light scattering from magnons in CsCoBr₃ has been measured for temperatures well below the upper antiferromagnetic 3D ordering temperature of T^l_N = 28 K. These experiments reveal multiple magnon features of energies in the range 90 to 170 cm^-1 similar to those found in CsCoCl₃ but previously unobserved for the bromide. Prominent features in the spectrum and their temperature dependence are described in terms of a recent theory by Shiba. Other, weaker features are explained by a simple extension of the theory to include fluctuations. A new band is observed at 178 cm^-1, whose intensity drops sharply prior to the lower 3D ordering transition at T^∥_N = 10 K. This band is assigned to magnon-phonon combination scattering.     

Spectrum and intensity of light scattered from SF6 along the coexistence curve

Our two groups have measured independently the “Rayleigh linewidth” (Γ), the reduced compressibility (??/?μ)_T, and the pressure (P) of SF₆ along the liquid and vapor sides of the coexistence curve. We find that (??/?μ)_T = 1.67 × 10^-10 (1 - T/T_c)^{-1.22 ± 0.015}g²erg^-1cm^-3 and (?P/?T)lχ = (7094 ± 0.1) × 10⁵ dyne/cm² ° We analyze our linewidth measurements in terms of the Kadanoff-Swift-Kawasaki mode-mode coupling theory using estimates for the viscosity and correlation range.     

Deep levels in gallium arsenide by capacitance methods

The three capacitance methods, i.e., TSCAP, PHCAP, and transient capacitance measurements, are applied to determine electronic properties of deep levels inn-GaAs. In the boat-grown wafer detected are the 0.30 eV electron trap withN _T =3.6×10¹⁶ cm^?3 andS _n =2.4×10^?15 cm², and the 0.75 eV electron trap withN _T =2.0×10¹⁶ cm^?3 andS _n =1.2×10^?14 cm². In the epitaxial wafer, the 0.45 eV hole trap is detected withN _T >1.5×10¹³ cm^?3 andS _p =1.4×10^?14 cm² as well as the 0.75 eV electron trap withN _T =2.4×10¹³ cm^?3.     

Influence of interchain coupling on the one-dimensional magnon Raman spectrum of CsCoBr3

Light scattering from magnons in CsCoBr₃ has been measured for temperatures well below the upper antiferromagnetic 3D ordering temperature of T^l_N = 28 K. These experiments reveal multiple magnon features of energies in the range 90 to 170 cm^-1 similar to those found in CsCoCl₃ but previously unobserved for the bromide. Prominent features in the spectrum and their temperature dependence are described in terms of a recent theory by Shiba. Other, weaker features are explained by a simple extension of the theory to include fluctuations. A new band is observed at 178 cm^-1, whose intensity drops sharply prior to the lower 3D ordering transition at T^l_N = 10 K. This band is assigned to magnon-phonon combination scattering.     

3 MeV electron irradiation-induced defects in CuInSe2 thin films

3 MeV electron irradiation induced-defects in CuInSe₂ (CIS) thin films have been investigated. Both of the carrier concentration and Hall mobility were decreased as the electron fluence exceeded 1×10¹⁷ cm⁻². The carrier removal rate was estimated to be about 1 cm⁻¹. To evaluate electron irradiation-induced defect, the electrical properties of CIS thin films before and after irradiation were investigated between 80 and 300 K. From the temperature dependence of the carrier concentration in non-irradiated thin films, we obtained N_D=1.8×10¹⁷ cm⁻³, N_A=1.7×10¹⁶ cm⁻³ and E_D=18 meV from the SALS fitting to the experimental data on the basis of the charge balance equation. After irradiation, a new defect level was formed, and N_T0=1.4×10¹⁷ cm⁻³ and E_T=54 meV were also obtained from the same procedure. From the temperature dependence of Hall mobility, the ionized impurity density was discussed before and after the irradiation.     

EHD-photoluminescence kinetics in doped Ge

Measurements of the LA-phonon assisted line kinetics of the EHD photoluminescence in As- and Sb-doped germanium with impurity concentrations n_D = 10¹⁵ ? 10¹⁷ cm^?3 are presented. These kinetics are found to be strongly dependent on the excitation level at 4.2 K. From the experimental results and a simplified kinetic equation the EHD “diffusion length” in Ge:As sample with n_D = 2 × 10¹⁶ cm^?3 is estimated to be L_D ? 0.34 mm which is consistent with previous results.     

Intervalley transfers of hot electrons in silicon below 77 K

Intervalley rate transfer along 〈100〉 directions is deduced from conductivity measurements versus electric field for different impurity concentrations N_D-N_A at lattice temperatures T ? 77 K. The maximum rate transfer plotted versus T reaches 1 at T < 25 K and does not depend on N_D-N_D for N_D-N_A ? 2 × 10¹⁴crmcm^?3.     

An experimental study of the collisional broadening of the Na-D lines by Ar and N2 perturbers in flames and vapor cells—II. The line wings

In this paper, we report on measurements of the fluorescence-excitation profile of the red Na-D₁ line wing from about 1 cm^?1 to 1100 cm^?1 and of the blue Na-D₂ line-wing from about 1 cm^?1 to 600 cm^?1, with respect to the corresponding line centre. We have also measured the fluorescence-excitation profile of the red Na-D₂ and blue Na-D₁ inner (overlapping) line wings from 1 cm^?1 with respect to the centre of each of the lines. All these wings were measured in several premixed, laminar, shielded H₂O₂Ar and H₂O₂N₂ flames at 1 atm (1400 K ? T ? 2300 K). We also measured these wings in a vapor cell containing Ar or N₂ perturbers (T ～ 480 K, p ～ 0.4 atm) in order to determine the influence of temperature on these wings. Using a tunable CW dye laser as excitation source, we determined the fluorescence-excitation profiles by measuring the total fluorescence intensity while tuning the laser wavelength. In order to specify the contributions that the different kinds of major flame perturbers (Ar, N₂, H₂O) make to the wings, we compared the wing profiles measured in various flames of different flame-gas compositions. In this comparison, the wing profiles were normalized with respect to the line-centre. We compared our measurements of far red Na-D₁ and blue Na-D₂ line-wings ($\text{Δσ ? 30}\text{cm}{}^{\mathrm{?1}}$) specified to Ar perturbers (at T = 500 K and T = 2000 K) with the results derived from quasi-static theory using available interaction potential data. In the case of Ar perturbers at T = 500 K, we observed a satellite at about 8 cm^?1 from the line-centre on the red Na-D₁ wing: this satellite was absent at T = 2000 K. The position of this red satellite was explained with the help of a set of “modified” potentials, which were constructed for interpreting the collisional Na-D broadening- and shift-rates deduced from our line-core observations and which were reported in Part I of this paper.     

Anomalous Cs I 5d-5⨍ lineshape in a non-debye plasma

Laser-induced cesium plasmas were diagnosed by emission spectroscopy, yielding electron densities in the range N_e = 10¹⁶?5 × 10¹⁷ cm^-3 and electron temperatures in the range T_e = 0.2-1 eV. The experimental lineshapes for T_e = 0.5 eV were found to be in good agreement with theory. For the more strongly coupled plasmas at N_e = 1-2 × 10¹⁶ cm^-3 and T_e = 0.2 eV, however, the Cs I 5d-5? lineshape was more asymmetric than predicted.     

Temperature-dependent light scattering from magnetic excitons in TlCoF3

Raman spectra of antiferromagnetic thallium cobaltous fluoride have been obtained with 4579A argon ion laser excitation at temperatures from 4°K to T_N = 94 ± 2°K. The features observed consist of six Co²⁺ excitons ranging in energy from 325 to 1070 cm^-1, at two-magnon peak with low-temperature energy of 315 cm^-1, and a one-magnon feature whose 4°K energy is 37 cm^-1. The energy and linewidth of the one-magnon scattering has been measured from 4°K to about 0.8 T_N; it is found that the magnon becomes critically damped at about 0.8 T_N, in good agreement with our previous observations on RbCoF₃. The Co²⁺ excitons observed at 325, 380, 410, 730 (weak), 960, and 1070 cm^-1 agree in energy quite well with the KCoF₃ levels calculated by Buyers, Holden et al. as 340, 400, 467, 767, 967 and 1050 cm^-1.     

Carrier concentration dependence and temperature dependence of mobility in silicon (100) N-channel inversion layers at low temperatures

The carrier concentration (N_s) dependence of electron mobility in Si (100) inversion layers has been measured at temperatures T = 1.5?70K for high- and low-mobility MOSFETs. An extrinsic term is observed in the T-dependent part of the scattering probability, τ^?1_T. At T = 4.4 K, τ^?1_T depends on N_s as N^?1.9_s in low mobility samples. In high-mobility samples, τ^?1_T increases with increasing N_s in high N_s region while τ^?1_T ∝ N^?1.6_s in low N_s region. The N_s-dependence of τ^?1_T becomes weaker with increasing T in both of low- and high-mobility samples. At N_s = 3 × 10¹² cm^?2, τ^?1_T depends on T as T^1.8 in low-mobility samples and τ^?1_T ∝ T^2.0 in high- mobility samples at T 5 K.     

Defect formation in tellurium in various gravity conditions

The effect of gravity (from micro-to a rather high gravity, 5g ₀) acting during tellurium crystallization on the concentration of neutral (N _D ) and electrically active (N _AD ) acceptor-type structural defects in samples grown both under complete remelting of the starting ingot and under directed seed recrystallization of an ingot was studied. The concentrations N _AD and N _D and their distribution over the sample length were derived from the electrical characteristics (conductivity and the Hall effect) measured along the ingots in the temperature range 1.6–300 K. The contributions of various mechanisms to hole scattering were found from an analysis of the temperature behavior of the mobility. The results obtained were compared with the characteristics of samples grown following a similar program under normal conditions. The presence of N _AD defects is characteristic of the initial crystallization stage of all samples. N _AD is substantially lower (N _AD ～ 10¹⁵ cm^?3) than N _D ～ 10¹⁸ cm^?3 and decreases exponentially in the course of sample crystallization. Complete remelting under microgravity revealed indications of strong supercooling and spontaneous crystallization, as well as spatial oscillations of the electrical resistivity over the sample length caused by N _D modulation. These observations are related to the specific features of the melting and crystallization in zero gravity, namely, the melt breaking away from the wall of the ampoule and the increasing role of Marangoni convection.