Change In Ionization Energy Research Articles

Evaluation of impurity content by Hall effect analysis in CdS

Carrier concentration and Hall mobility have been analyzed for defect-introduced CdS in the temperature range from 10 to 300 K. Defects were introduced by 10 MeV electron irradiation into undoped CdS in which impurity conduction appears. An iterative method was used for the Hall mobility analysis. The overall agreement between the carrier concentration and Hall mobility analyses has been excellent. The following results are obtained: (1) Impurity conduction appears in CdS containing concentrations as low as 2.8×10 15 donors/cm 3 and 1×10 14 acceptors/cm 3. (2) The piezoelectric constants are 0.207±0.005 and 0.152±0.005 for the directions parallel and perpendicular to the c-axis, respectively. (3) Irradiation with 10 MeV electrons introduces mainly acceptor-type defects and suppresses impurity conduction. (4) The acoustic phonon deformation potential increases with irradiation. (5) Donor ionization energy changes with acceptor concentration as E D=33−3.9×10 -5 N 1/3 A meV.

Photoelectron spectra of the valence d shells of Tl(I), In(I), Pb(II) and Sn(II) Halides

The elements Zn, Cd, Hg, In, Tl, Sn and Pb all possess d electrons which fall within the ionization energy range normally considered as the valence region but which are essentially atomic in nature. The valence d −1 ionized states of the halides of the first three of these elements have already received some attention in the literature and here ionization from the corresponding d shells of the vapour-phase halides of the remaining four elements is reported. Spectra are shown to be consistent with an atomic description for the orbitals and ionization energies are shown to be reasonably described by a simple electrostatic model. Changes in ionization energy which occur with change in substituent for a particular metal are consistent with the chemical shift model. For the Tl halides fine structure is observed in the 2 D multiplet. This is interpreted in terms of a ligand field model and an analysis is proposed on this basis.

Effect of Pressure on the Energy Levels of Impurities in Semiconductors. I. Arsenic, Indium, and Aluminum in Silicon

The changes in resistivity of silicon samples containing group III and group V impurities have been measured at hydrostatic pressures up to 6000 kg ${\mathrm{cm}}^{\ensuremath{-}2}$ at 50\ifmmode^\circ\else\textdegree\fi{}K. The changes are explained by a dependence on pressure of the ionization energy of the majority impurity center. The results indicate that the arsenic energy level moves toward the conduction-band edge at a rate of approximately 5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ eV ${\mathrm{kg}}^{\ensuremath{-}1}$ ${\mathrm{cm}}^{2}$. The energy levels for indium and aluminum move away from the valence-band edge at rates of about 5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ eV ${\mathrm{kg}}^{\ensuremath{-}1}$ ${\mathrm{cm}}^{2}$ and 1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ eV ${\mathrm{kg}}^{\ensuremath{-}1}$ ${\mathrm{cm}}^{2}$, respectively. Corrections for the changes in mobility with pressure have been applied for the $n$-type sample. The motion of the arsenic energy level is explained by a change in dielectric constant and effective mass with pressure, and indicates a change in the average effective mass of less than 1% in 5000 kg ${\mathrm{cm}}^{\ensuremath{-}2}$. The very small changes in ionization energy, while expected, are to be contrasted with the much larger changes found for the deep-lying levels produced by elements such as gold.

The effect of pressure on the properties of germanium and silicon

Measurements of the pressure dependence, in germanium and silicon, of the intrinsic resistivity, the fundamental absorption edge, the carrier mobilities, the magnetoresistance coefficients, and the dielectric constant are reviewed, and an explanation based on the shift of the band edges presented. Experimental evidence for similar behavior of corresponding band extrema in germanium, silicon and the intermetallics is given. The cases of the (111) and (100) minima in germanium and silicon and the Ge-Si alloys are discussed in detail. The results of measurements of the change of ionization energy of shallow and deep lying impurity levels in germanium and silicon are also reviewed.

Theory of Interstitial Impurity States in Semiconductors

The ionization energy and expectation value of the radius corresponding to the states of several interstitial impurities in Ge and Si are calculated. The range of the valence electron of the impurity is divided into two regions; an inner region, which is treated microscopically, and an outer region, which is treated macroscopically. The separation radius, which is primarily a function of the host crystal, is a parameter of the calculation. At a critical separation radius a rapid change of ionization energy and wave-function results. The calculations are carried out for several impurities in column I of the periodic table.