Magnetic quantum oscillations in nanowires

Analytical expressions for the magnetization and the longitudinal conductivity of nanowires are derived in a magnetic field, B. We show that the interplay between size and magnetic field energy-level quantizations manifests itself through novel magnetic quantum oscillations in metallic nanowires. There are three characteristic frequencies of de Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) oscillations, F = F(0)/(1 + gamma)(3/2), and F(+/-) = 2F(0)/|1 + gamma +/- (1 + gamma)(1/2)|, in contrast with a single frequency F(0) = S(F)plankc/(2pie) in simple bulk metals. The amplitude of oscillations is strongly enhanced in some magic magnetic fields. The wire cross-section area S can be measured using the oscillations as S = 4pi(2)S(F)plank(2)c(2)/(gammae(2)B(2)) along with the Fermi-surface cross-section area, S(F).     

Free exciton luminescence lineshape of Hg0.3Cd0.7Te

The photoluminescence spectrum of Hg_0.3Cd_0.7Te at 77K includes a narrow, high energy free exciton line. This experimental spectrum is in good agreement with the theoretical free exciton lineshape, the Gaussian broadening of this line is due to alloy inhomogeneity, and the binding energy of the bound exciton with respect to the free exciton at 77K is 13 ± 4 meV.     

High conversion efficiency Hg0.77Cd0.23Te spin-flip Raman laser

Peak external conversion efficiencies of several percent have been measured in the 10 μm region when a CO₂ laser is used to pump a Hg_0.77Cd_0.23Te spin-flip Raman laser. Strong pump depletion is observed in the experiments. Quantum oscillations from the n = 0, 1 and 2 Landau levels are observed in the tuning characteristics. At 710 G the spontaneous linewidth is measured to be 8 G. Large effects due to conduction band nonparabolicity are observed.     

Investigation of pulsed laser ablation process of Hg0.8Cd0.2Te

The vaporization threshold was measured under the irradiation of 1.064-μm, 10-ns pulsed laser. Then we calculated the vaporization temperature based on the conservation law of energy and analyzed the vaporization time based on our established model. These results coincided well with the information from the micrograph of scanning electron microscope (SEM) and the spectra of the plasma. Besides, the laser ablation rate was also computed and discussed theoretically.     

Pulse characteristics of Hg0.8Cd0.2Te n +-p junctions

The pulse characteristics of Hg_0.8Cd_0.2Te n ⁺-p junctions are investigated. It is shown that the shape of the voltage pulse appearing in a junction on passage of a forward (reverse) current is determined by the recombination (generation) of nonequilibrium electrons in the hole region. An increase in the current pulse causes the appearance of an electric field, which draws electrons into the interior of the base region, and leads to variation of their lifetime because of the complex structure of the n ⁺-p junction. Zh. Tekh. Fiz. 67, 130–133 (July 1997     

Observation of a new gettering mechanism in (Hg,Cd)Te

A new gettering mechanism is proposed for substitutional impurities which diffuse by an interstitial process. In this mechanism, an externally imposed gradient of self interstitials generates a gradient in impurity interstitials leading to the segregation of fast diffusing impurities to low interstitials, high vacancy regions. Data are presented to support this model in (Hg, Cd)Te alloys, as well as explicitly rule out gettering by dislocations, by segregation to precipitates, or by enhanced solubility arising from the interaction of the impurity with a varying Fermi level.     

A high-sensitivity near-millimeter-wave photoconductive detector using [Hg, Cd]Te

In an earlier paper [1], we reported the observation of photoconductivity from free-carrier absorption in [Hg, Cd]Te. By using samples of [Hg, Cd]Te with different electrical and alloy properties, we have improved the near-millimeter-wave (NMMW) responsivity by over two orders of magnitude. At 1.6 K a best sample responsivity of about 185 V/W and a bandwidth of over 5 MHz have been measured. This responsivity corresponds to a Johnson-noise-limited noise-equivalent-power (NEP) of 1.6 × 10^–12 . Another sample of similar compposition yielded an NEP of 1.8 × 10^–12 and a 25 MHz bandwidth. These results coupled with a wide spectral sensitivity [1] indicate that [Hg, Cd]Te NMMW detectors compare very favorably with similar InSb detectors [2].     

Thermal noise in Hg0.795Cd0.205Te detectors for large biasing fields

Thermal noise in Hg_0.795Cd_0.205Te detectors is estimated for large biasing fields at a lattice temperature of 77 K, by computing the correlation functions of the velocity fluctuations with the Monte Carlo technique. The noise temperature for current components transverse to the field is almost independent of the field, but that corresponding to the parallel component increases by a factor of about 1.3 at 50 V/cm and by a factor of 3.0 at 300V/cm. The thermal noise voltage for a detector of 85 resistance increases from 0.6nV/Hz^1/2 at low biasing fields to about 3nV/Hz^1/2 at a field of 300 V/cm. The noise power is also found to remain constant up to about 75 GHz, and it decreases thereafter by a factor of 0.25 for doubling of the frequency.     

A comparison of the dominant Auger transitions in p-type (Hg,Cd)Te

We predict that the Auger hole-hole collision process involving a transition from the light hole band to the heavy hole band is an important recombination mechanism in non-degenerate p-type (Hg,Cd)Te. This is based on a comparison of the calculated lifetime for this mechanism with that due to the electron-electron collision mechanism discussed by Beattie and Landsberg which involves only the heavy hole valence band. We have estimated the ratio of the intrinsic lifetimes of these two mechanisms by approximating the integrals appearing in the lifetime expressions. We have determined the range of composition, temperature and doping density over which the Auger lifetime in p-type (Hg,Cd)Te is controlled by the light hole mechanism.     

Computer simulation of non-cooled long-wavelength multi-junction (Cd,Hg)Te photodiodes

A numerical analysis of long-wavelength multi-junction photodiodes constructed from Cd_xHg_1−xTe heterostructures is performed. The standard Newton iterative scheme is applied to solve the non-linear system of continuity equations and the Poisson equation. All quantities are expressed as a function of electric potential and quasi-Fermi levels. Results of computations are presented in the form of maps and plots illustrating spatial distributions of electrical potential and responsivity. Such an illustration enables us to explain the effect of reverse sign of the photovoltage occurring in photoelectric devices being manufactured.     

Carrier freezeout in n-on-p Hg0.7Cd0.3Te photodiode and acceptor level determination

0.7 Cd_0.3Te photodiodes at temperatures lower than 25 K. The freezeout was seen under the conditions that interband tunneling dominates the current in the photodiode and that avalanche ionization does not take place. These conditions are fulfilled at temperatures lower than 25 K and reverse bias voltages around 3 V. An acceptor level of about 4 meV was determined for p-type Hg_0.7Cd_0.3Te with N_A-N_D∼10¹⁶ cm^-3 from the temperature dependence of the photodiode resistance governed by carrier freezeout. The difficulties in observation of carrier freezeout in Hg_1-xCd_xTe with a larger composition ratio x or higher doping concentration are discussed. Received: 21 November 1996/Accepted: 15 April 1997     

Electron states in inversion layers on the small-gap semiconductor Hg1−x Cd x Te

Summary The subband structure of the narrow-gap semiconductor Hg_1−x Cd _x Te is investigated theoretically at finite temperature by a modified sixbandk·p model based on the effective-mass approximation. A study of the complete surface energy spectrum is reported. The mobile, bound and resonant states are treated by considering energy states in a large quantum box. The theory is applied to cases with strong interband interaction when the resonant character of the subband states is prominent. The authors of this paper have agreed to not receive the proofs for correction.     

Raman gain,effectiveg-value and spontaneous spin-flip Raman linewidth in Hg0.77Cd0.23Te

We report on measurements of spin-flip Raman gain inn-Hg_1?x Cd _x Te (x=0.23, carrier density 1.0×10¹⁵cm^?3) as a function of the magnetic field up to 1.6T. The measurements were carried out by a small signal gain technique at a temperature of 1.8 K. Furthermore, the measurements yield lineshapes and linewidths of the spontaneous scattering and allow a precise determination of the effectiveg-value. The highest gain observed is 0.2 cm/W. The band edge value of the effectiveg-value is ?93.2 and the widths of the symmetric lines are between 18 and 120 G, depending on the magnetic field.     

Magnetic field dependent magnetization oscillations in two-dimensional quantum electron systems

A simple relationship between amplitudes of magnetization oscillations is presented as result of a single-electron Josephson junction in a two-dimensional quantum electron system with a perpendicular magnetic field.