摘要:

AbstractBy the projection operator technique the non‐Markovian kinetic equation for the density matrix of a crystal impurity centre in an external electromagnetic field is derived, taking into account the electron–phonon interaction. The analytical solutions of this equation are obtained for the external field as an ultrashort pulse and in the case of a monochromatic w

ISSN:0370-1972    

DOI:10.1002/pssb.2221370226

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe theory of point defect ionization in semiconductors by the streamer discharge electric field is developed. It is shown that due to high streamer velocity and sharp spatial inhomogeneity of the electric field defect ionization is a fast quantum process with a large energy uncertainty of particles involved and, hence, it does not occur by tunneling. Localized wavefunctions are described by the quantum defect method. The ionization probability is calculated and its straightforward dependence on the velocity and the form of the streamer field and the defect parameters is determined. As in the case of interband transitions considered in the first work the ionization probability is an increasing function of the streamer velocity and the field steepness.

ISSN:0370-1972    

DOI:10.1002/pssb.2221370227

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe question of localization is examined in a tight‐binding Hamiltonian. The present method is based on a self‐consistent theory reproducing correctly the band edge in the limit of zero disorder. Randomness is introduced also in the off‐diagonal elements. In a purely diagonal disorder it is found that the results for the critical disorderWcfor which the Anderson transition appears are in good agreement with other theories while for a purely off‐diagonal disorder the states around the middle of the band remain e

ISSN:0370-1972    

DOI:10.1002/pssb.2221370228

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThermoluminescence and X‐Ray fluorescence of single crystal of CaF2:Nd are studied earlier. Since the major emission is in the infrared, attention is denoted to this region only. Although, there are reports that strong emission in the visible is also observed, detailed results are not available in the literature. In this paper, thermoluminescence (TL) emissions in the UV and visible region are studied in the temperature range between liquid nitrogen temperature and 400 °C. Several parameters associated with the TL emission are also calculated. A tentative mechanism for concentration dependence of the 315 °C TL peak is sugges

ISSN:0370-1972    

DOI:10.1002/pssb.2221370229

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractExpressions for the thermopower in quasi‐two‐dimensional semiconductor quantum well structures are obtained in the extreme quantum limit when electrons are scattered by acoustic phonons via deformation potential coupling, polar optical phonons, and ionized impurities. Numerical results are given for the size dependence of thermopower. It is found to be enhanced over its bulk value for lower values of well thickness. The contributions from individual scattering mechanisms are found to increase with the increase of temperat

ISSN:0370-1972    

DOI:10.1002/pssb.2221370230

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractFirst investigations are reported on the temperature dependence of the dc‐conductivity atT= = 0.05 to 300 K on neutron‐transmutation‐doped (NTD) n‐GaAs in the vicinity of the metalinsulator transition (MIT). At a medium compensation ofK= 0.60 to 0.77 the MIT takes place at the critical electron concentration ofnc= 2.3 × 1016cm−3. On the dielectric side of the MIT in the variable‐range hopping regime (VRH) atT≦ 10 K the conductivity obeys the equation σ(T) = σ0exp [— (T1/T)1/2] and not the Mottlaw. The experimental valuesT1are for all samples much smaller thanT1theorfor isolated shallow impurities and scale down according toT1= =T1*(1 ‐n/nc)1.6±0.4withT1* = 5.9 K by approaching the MIT. This behaviour is due to the divergency of the localization radiusaand the static DK ϵ0at the MIT. The obtained linear In σ —T−1/2law over about 2.5 orders of magnitude in temperature variation and more than three orders of magnitude of variation in conductivity is interpreted in the frame of a Coulomb gap with vanishing density of states at the Fermi level, as predicted by Efros and Shklovskii. The pre‐exponential factor ϱ0= σ0−1shows also scaling behaviour according to ϱ0= ϱ0*(1 ‐n/nc)1.2±0.4and a value of ϱ0* = 2.2 Ω cm. Atn→ncσ0= ϱ0−1reaches the value of Mott's minimal metallic conductivit

ISSN:0370-1972    

DOI:10.1002/pssb.2221370231

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe influence of photon recycling (PR) onto the minority carrier distribution in double heterostructures is investigated. For non‐perfect optical confinement of the luminescence radiation in the active zone, the corresponding integro‐differential equation (without drift term) of the diffusion model cannot longer be solved exactly. The enlargement of the radiative lifetime, as measured in photoluminescence experiments, e.g., is calculated approximatively by means of perturbational methods. Particular attention is devoted to the dependence of this enlargement due to PR upon the thickness of the active zone. In very thin active zones, PR should play a minor role due to the loss of luminescence radiat

ISSN:0370-1972    

DOI:10.1002/pssb.2221370232

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

ISSN:0370-1972    

DOI:10.1002/pssb.2221370233

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

ISSN:0370-1972    

DOI:10.1002/pssb.2221370201

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY