ISSN:0033-7579    

DOI:10.1080/00337577008234954

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

ISSN:0033-7579    

DOI:10.1080/00337577008234955

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

When highly pure additively colored KCl crystals are heated in the dark at about 300 °C, F-band is suppressed and a long wavelength (LW) band at 730 nm is formed. The centers responsible for this LW band are mainly colloidal particles of potassium. The colloidal centers also give a Lorentzian EPR line withg= 1. 9998 and half width 2. 5 gauss. A large electronic conductivity due to thermionic emission of electrons from the colloids into the conduction band of the KCI crystal is observed. If the crystals contain background divalent impurity, on heating, F-centers combine with impurity-vacancy pairs to form ScottR'-centers. ScottR'-centers do not show EPR absorption, suppress the ionic conductivity by a large factor and give rise to a broad LW optical absorption band.

ISSN:0033-7579    

DOI:10.1080/00337577008234956

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Interaction of photoexcited carriers with optical phonons can produce oscillations in the spectrum of photoconductivity. The separation between successive minima is related to the phonon energy. The oscillation occurs when the excited carriers lose their energy rapidly by the emission of optical phonons and do not exchange energy with acoustical phonons effectively during their lifetime. Under such conditions, the energy distribution of carriers varies with photon energy periodically within the range of one optical phonon energy from the edge of the energy band, leading to a variation of photoconductivity either through an energy dependence of the carrier mobility or through an energy dependence of the carrier lifetime. Oscillations of this nature have been observed in a variety of semiconductors and have been found in intrinsic as well as extrinsic photoconductivity and photomagnetic effect. Studies of the oscillations have provided information on the energy band, excitons, impurity levels and phonon energy. Under high magnetic fields, additional structures in the spectrum can be observed which are associated with the Landau levels. The effect provides an additional means for the study of Landau levels and quantum transport.

ISSN:0033-7579    

DOI:10.1080/00337577008234957

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

For fiω + 4Δ andkBT≫ 4Δ, where 4Δ is the energy difference between the donor ground state and the next higher energy state, the resonance relaxation rate ττ−1for the scattering of phonons by bound donor electrons in doped Ge or Si, is proportional to ω2. For fiω < 4Δ andkBT <4Δ, the elastic scattering term off the ground state dominates and one obtains ω4-dependence for τt,−1. The ω4-dependence of ττ−1gives reasonable values of the resonance scattering strength, which is proportional to the fourth power of the shear deformation potential.

ISSN:0033-7579    

DOI:10.1080/00337577008234958

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The nature of the transition from insulator to metal induced by increasing donor impurity concentration in Si and Ge is investigated. Only the low temperature regime, in which thermal excitation of carriers is unimportant, is considered. A review is given of present theoretical models of the effect of electron correlations on the transition, and a summary of current experimental information is given. Effects of the random spatial distribution of the impurity atoms is discussed. A percolation model is developed, cluster size distributions as a function of impurity concentration calculated by Monte Carlo techniques are described, and the model is used to interpret the DC transport properties of Si and Ge. The model also clearly maps out the observed development of ESR line shapes through the transition region and shows that the ESR delocalization transition occurs at lower concentration than the transition in DC transport properties. The percolation model is related to other recent attempts to allow for the random distribution of impurity atoms.

ISSN:0033-7579    

DOI:10.1080/00337577008234959

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The paper deals with the design and lay-out of a horizontal epitaxial system capable of holding 4–6 slices simultaneously. Epitaxial films prepared by hydrogen reduction of silicontetrachloride are of good quality for fabricating planar devices.

ISSN:0033-7579    

DOI:10.1080/00337577008234960

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Available results of the doping effects on self-and impurity-diffusion in Ge and Si are analysed quantitatively, showing that self-interstitials responsible for high temperature diffusion in Si are amphoteric with an acceptor level above the middle of the band gap and a donor level below the middle of the band gap. In Ge the vacancies are responsible for the diffusion mechanisms and have an acceptor level near the edge of the valence band. Approximate values for the donor and acceptor levels of the defects in Ge and Si are also given.

ISSN:0033-7579    

DOI:10.1080/00337577008234961

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

All intrinsic semi-conducting elements at absolute zero of temperature have their valence electrons occupying completely the valence band, the electrons being localized as co-valent spin pairs. At non-zero temperature, a fraction of these pairs gets broken, with the corresponding electrons thermally excited into the conduction band. The conduction electrons can be considered ‘non-localized’ and the process of spin decoupling, one of configurational entropy gain for the whole system. On considering the electronic wave function as mixed in character due to electrons ‘localized’ and ‘non-localized’, one can write it as a superposition of a metallic and a cevalent wave function. The resultant Hamiltonian permits one to calculate the configurational entropy of electrons in semiconducting elements and some semiconducting compounds. It is this contribution which is shown to be the reason of excess entropy of fusion of all semiconductor elements. The analysis elucidates some of the anomalous electronic behavior of semimetallic and semiconducting compounds.

ISSN:0033-7579    

DOI:10.1080/00337577008234962

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The method given by Pekeris for He-atom and generalized recently by Frost for three-particle system is applied to calculate the binding energies of excitons bound to ionized donors and acceptors. The calculations are carried out for different values of γ =me*/mh*whereme*andmk* are the effective masses of the electron and the hole respectively. For ionized donors the system is stable for γ < 0. 32. In semiconductors where excitons are bound to ionized acceptors the value of γ > 0. 227 is necessary to provide a stable system.

ISSN:0033-7579    

DOI:10.1080/00337577008234963

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor