Anderson transition criterion as found from intervalley acoustoelectron relaxation in heavily doped n-Si

Acoustic measurements are shown to be useful for the study of metal-dielectric transition in semiconductors. Squared core wave function of electron on donor centers in Si calculated from acoustic data is found to decrease at high donor densities. Critical impurity concentration is close to that obtained in other ways.     

Estimation of plasma frequency from IR reflectivity in doped GaAs

The influence of the phonon-plasmon coupling on the IR reflectivity spectra of doped GaAs is examined for the range of plasma frequencies which are close to the optical phonon frequencies. An analytic expression for the plasma frequency in terms of the frequencies of the reflectivity minima, which requires knowledge of the dielectric constant at the reflectivity minima and the carrier lifetime, is obtained. Empirical relations are suggested to estimate the required dielectric constant. Lifetime is estimated by a graphical method. These relations are used to estimate the plasma frequencies from the reported reflectivity spectra of doped GaAs samples.     

Infrared transmissivity of heavily doped contact layers on extrinsic silicon IR-detectors

The infrared transmissivity of heavily dopedp-type contact layers on silicon was studied in the 3–5 μm and 8–14 μm wavelength range in order to optimise the layer thickness and doping concentration for antireflection coating. The transmissivity of surface layers and buried layers was computed taking into account the free carrier optical dispersion by the Drude theory and corrections due to intervalence band transitions as well as multiple reflections and interferences in the layer. The computations are in quantitative agreement with measurements on contact layers formed by multiple boron implantation. It was found that the free carrier absorption loss completely cancels the gain due to the antireflection effect for a surface layer. Transmissivities of around 73% may be obtained by a buried heavily doped layer.     

Anomalies in the reflectivity around 3.6 eV of ZnS heavily doped with Mn2+-ions

The wavelength modulated reflectivity of ZnS (23% Mn) shows additional structure below 100 K which is correlated to a magnetic ordering effect.     

Electron mobility in heavily doped silicon

We have calculated the mobility of conduction electrons in heavily doped n-type silicon. The Thomas-Fermi screening and the Born approximation are employed. The dependence of the effective mass on carrier density determined empirically is considered. The results are compared with experimental data obtained recently.     

Photoluminescence of heavily doped n-InP

Photoluminescence and excitation spectra of weakly compensated n-type InP layers doped with tin in the density range from 3 × 10¹⁷ cm^-3 to 2 × 10¹⁹ cm^-3 are measured at T=2 K in order to get experimental informations about the influence of doping on important material parameters such as the band gap energy and the position of the quasi-Fermi level of electrons. The results derived from these investigations are compared with those obtained of relevant many-body theories to heavily doped semiconductors. Using RPA and Klauder's best (fifth) approximation the doping induced gap shrinkage of uncompensated n-InP is calculated. The comparison between theory and experiment yields the conclusion that for standard direct gap AIII-BV compounds such as InP and GaAs the compensation in principle expected has to be taken into the theoretical considerations. Moreover, we first present a “semianalytical” treatment of Klauder's multiple scattering approach which makes this theory easily applicable to other problems as for instance calculations of the luminescence line-shape of doped semiconductors.     

Fano resonance in heavily doped porous silicon

Unexpectedly, the Fano resonance caused by the interference of continuum electron excitations with the longitudinal optical (LO) phonons was observed in random porous Si by Raman scattering. The analysis of the experimental data shows that the electron states trapped at the Si SiO₂ interface dominate in the observed Raman scattering. The gap energy associated with the interface states was determined. Copyright © 2011 John Wiley & Sons, Ltd.     

Mott transitions in heavily doped magnetic semiconductors

A generalization applicable to magnetic semiconductors is proposed for the Mott criterion for transitions of heavily doped semiconductors from an insulating into a highly conducting state. Based on this generalization, a study is made of insulator-metal transitions in a ferromagnetic semiconductor associated with temperature variations and of insulator-metal transitions in an antiferromagnetic semiconductor acted on by a magnetic field. These results are of independent interest for nondegenerate semiconductors as well, since they yield the temperature and field dependence for the impurity state radii and for the energies and magnetizations of unionized donors or acceptors. Fiz. Tverd. Tela (St. Petersburg) 40, 433–437 (March 1998)     

Nuclear spin-lattice relaxation in heavily doped silicon

The anomalous temperature and magnetic field dependences of spin-lattice relaxation time were observed in heavily phosphorus doped silicon. These anomalies should be attributed to the dynamical nature of the highly correlated electron gas which contributes to metallic impurity conduction.     

Infrared reflectivity of BaMnF4

The polarized reflectivity of BaMnF₄ single crystals was measured in the 20–600 cm^–1 range for temperatures from 10 to 300 K. The results were evaluated using Kramers-Kronig analysis to obtain the dielectric function. The number of active modes in the high temperature polar phase (T>T _i 250K) is in agreement with group-theoretical expectation. In the incommensurate phaseT<T _i the number of active modes increases more than two times. All the results are in reasonable agreement with previous Raman and far infrared data.     

Quantum oscillations in heavily doped bismuth chalcogenides

The observation of Shubnikov-de Haas and Hall oscillations in high-quality Bi_{2 ? x} Cu _x Se₃ single crystals is reported. Measurements carried out upon rotating the samples with respect to the magnetic field demonstrate that the oscillations originate from two-dimensional surface states in three-dimensional single crystals and are determined only by the perpendicular component of the magnetic field.     

Anomalous magnetoresistance in heavily antimony doped germanium

Anomalous magnetoresistance in heavily antimony doped germanium is studied down to 5 mK. The experimental results is reasonably interpreted within a framework of s-d interaction with a negative exchange constant. Electrons localized in a sense of Anderson are suggested to play a role of d electrons when Coulomb correlation is introduced.     

Thermoreflectance investigation of heavily doped silicon

The effect of the presence of high concentrations of dopants on the interband spectra of silicon has been studied by means of thermoreflectance. Heavy doping has been performed through ion implantation and eventually laser annealing. From the analysis of the thermoreflectance spectra a wide set of parameters characterizing in particular the E₁andE₂ structures has been obtained.     

Frequency shift of the plasma reflectivity minimum due to uniaxial stress in n-type silicon

The pronounced influence of 〈100〉 compressive stress on the frequency of the reflectivity minimum associated with free carrier dispersion has been measured for radiation polarized perpendicular or parallel to stress. Interpretation of the results in terms of the electron transfer model suggests that the phenomenon might be used to determine effective mass anisotropies in multivalley semiconductors.