摘要:

Polarized oscillatory magnetoabsorption spectra of exciton formation transitions in InSb have been measured under high resolution at liquid helium temperature. An unstrained high‐mobility sample 5 &mgr; thick and magnetic fields up to 39.1 kgauss were used. Diffraction grating dispersion for the region 3.7<&lgr;<6.0 &mgr; made possible a resolution of 1−7×10−4ev and the determination of absorption maxima to ±5×10−5ev. Sixteen minima were resolved withE⊥Bfor a field of only 5.0 kgauss. The initial interpretation of the detailed spectra obtained involved fitting theoretical spectra calculated from the theories of Kane, Luttinger, and Elliott‐Loudon in order to account for band nonparabolicities, valence band degeneracy effects, and exciton binding energies, respectively. The results experimentally established the light‐hole nonparabolicity, the valence band degeneracy effects for low magnetic quantum numbers, and the existence of high‐field excitons in InSb.

ISSN:0021-8979    

DOI:10.1063/1.1777027

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A new method in making single crystals of GaP and the preparation of diodes is described. Thep‐nluminescence and photoluminescence of undoped and Zn‐doped GaP are investigated and the light output of thep‐nluminescence as a function of temperature and excitation density is discussed. The spectral sensitivity of thep‐nphotovoltaic effect is recorded.

ISSN:0021-8979    

DOI:10.1063/1.1777028

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Experimental investigation of Faraday rotation in III–V compounds has exhibited a striking singularity at photon frequencies just below the energy gap. A quantum theoretical result associated with the direct transition has been developed to explain the phenomenon. The treatment has been extended to include forbidden transitions which are readily applicable to such materials as InAs, GaAs, and GaSb where interband transitions between the split‐off valence bands have been observed. The treatment for observing Faraday rotation by reflection has also been considered and experimental results in InSb at optical frequencies will be presented. The calculations have also been performed for degenerate semiconductors at low temperature.

ISSN:0021-8979    

DOI:10.1063/1.1777029

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Measurements of cyclotron resonance absorption have been made in the far infrared spectral region from 25−150 &mgr; on several III–V compounds at room and liquid‐nitrogen temperatures using steady magnetic fields as high as 75 kgauss. Forn‐type InSb, InAs, InP, and GaAs, the data yield information concerning the conduction electron effective mass at the bottom of the band and its variation with magnetic field. Experiments have also been carried out onp‐type InSb and corresponding information has been obtained for light holes. The dependence of the effective masses on both temperature and magnetic field can be satisfactorily interpreted in terms of Kane's theory for the band structure of these materials.Measurements of Faraday rotation and Voigt double refraction have been made in the spectral region between 15 and 25 &mgr; on a number of compound semiconductors at liquid‐nitrogen temperatures. Either experiment gives the effective mass of the free carriers if their concentration is known. If both experiments can be performed, the results can be combined to give both the effective mass and carrier concentration directly without recourse to electrical measurements.

ISSN:0021-8979    

DOI:10.1063/1.1777030

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Values of absorption constant covering the range 1 cm−1to 104cm−1have been derived from transmission measurements made on single‐crystal gallium arsenide. The absorption edge is very steep up to ∼4000 cm−1, where there is a knee beyond which the absorption increases relatively slowly with photon energy. The energy bands have been calculated using Kane's theory. From these a theoretical absorption curve has been obtained which shows very good agreement with the experimental data.Using semi‐insulating material, it has been possible to measure the shift of the edge with applied electric field. The effect is small (∼200‐&mgr; ev shift for 5000‐v/cm field) but is in good agreement with theory.

ISSN:0021-8979    

DOI:10.1063/1.1777031

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Conductivity in impurity bands is observed in gallium arsenide at low temperatures. The impurity banding phenomena observed inn‐andp‐type crystals are markedly different due to the wide divergence in their effective masses. In the temperature interval where the crystal conductivity is determined by conduction in the impurity band, resistivity ofn‐type material decreases with increasing magnetic field.The temperature dependences of carrier mobility indicate that at low temperature the impurity ions play the dominant role of the scattering centers. In order to investigate scattering processes more thoroughly, studies were made of the thermomagnetic Nernst‐Ettingshausen effects which are very sensitive to the scattering mechanism. It was found that, in the case of nondegenerate specimens at low temperatures, scattering by impurity ions dominates, and at high temperatures by acoustical lattice vibrations; scattering by acoustical lattice vibrations becomes dominant even at low temperature in specimens of high degeneracy. Scattering was also investigated in indium arsenide and indium antimonide.

ISSN:0021-8979    

DOI:10.1063/1.1777032

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Samples ofn‐type PbTe crystals with different electron concentrations (n=2×1017∼5×1019/cc) were prepared by impurity doping or by heating in the vapor of lead. The electrical properties of these crystals were independent of the kind of impurities and depended only on the electron concentration. The electron mobilities of our samples were proportional ton−⅓at 77°K, and ton−4/3at 4.2°K. As the conduction electrons in our samples are degenerate at these temperatures, the experimental results mentioned above suggests that the conduction electrons in PbTe crystals are scattered mainly by acoustical mode at 77°K and by neutral imperfections at 4.2°K.Since the electron mobility in PbTe becomes very large at 4.2°K (e.g., 1∼4×106cm2/v‐sec), this material is quite suitable for the experimental studies of the quantum transport phenomena. To investigate such phenomena, the Hall and magnetoresistive effects ofn‐type PbTe crystals were measured at 4.2°K in a pulsed magnetic field up to 170 kgauss. In the specimens with relatively low electron concentrations (e.g.,n≃3×1017/cc), the magnetoresistive effect had a single minimum at about 77 kgauss in a transverse magnetic field, and at about 55 kgauss in a longitudinal field. This minimum should correspond to the situation where the Landau level withl= 1 coincides with the Fermi level in the PbTe crystals.

ISSN:0021-8979    

DOI:10.1063/1.1777033

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The fundamental reflectivity spectrum of several III–V and II–VI semiconductors is discussed and compared with the reflectivity spectrum of the group IV semiconductors. A general feature of these spectra is the presence of two peaks within the fundamental absorption region. The lower energy peak, which corresponds to a maximum in the refractive index, can be split into a doublet. This peak is probably due to direct transitions between the valence band extrema in the [111] direction at the edge of the Brillouin zone (Lpoint) and the corresponding conduction band minima. The splitting of this peak corresponds to the spin‐orbit splitting of the valence band extrema (L3). The second peak corresponds to a maximum in the combined density of states for the transitions. The temperature dependence of these peaks is also discussed.

ISSN:0021-8979    

DOI:10.1063/1.1777034

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The experimental information relevant to the band structure of the compounds InSb, InAs, GaSb, GaAs, GaP, AlSb and some of their alloys is synthesized and interpreted in terms of a consistent theoretical picture which exploits the close relationship linking the band structures of the group 4 and 3–5 semiconductors. It is shown that the momentum matrix element determining the conduction band masses in those compounds whose edge is of symmetry type &Ggr;1, is nearly constant. Simple theoretical expressions, agreeing well with experiment, are derived for the corresponding effective masses and valence band spin‐orbit splittings, following Kane's theory for InSb. The dominant scattering mechanisms determining the transport properties are reviewed briefly. Arguments are presented which show deformation potential scattering to be unimportant relative to polar optical mode scattering. A heuristic treatment indicates that the relaxation time approximation can be applied reasonably to polar scattering for temperaturesT>ℏ&ohgr;l/K, where &ohgr;lis the longitudinal optical frequency. Multiband transport effects are discussed with special reference to the Nernst effect in GaAs and the electron mobility in GaSb. An explanation of the high‐temperature behavior of the Nernst coefficient in GaAs in terms of polar and intervalley scattering is proposed. The mobility in GaSb remains unexplained.

ISSN:0021-8979    

DOI:10.1063/1.1777035

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Dispersion relations for optical properties of solids, and a sum rule for the imaginary part of the dielectric constant, are reviewed and applications to semiconductors are described. Plasma frequencies, for which the real part of the dielectric constant vanishes, are associated with lattice vibrations, with free carriers, and with valance electrons. Gottlieb's infrared optical constants for LiF are in good agreement with the lattice vibration sum rule using unit effective charge. Dispersion relations for reflectivity have been used by Dixon to analyze optical constants ofp‐type PbTe in the infrared region where free‐carrier effects dominate. He finds an effective mass at room temperature which rises from 0.1mto 0.3mas the carrier concentration is increased from 3×1018to 1020cm−3. Morrison has measured the reflectivity of InAs, InSb, and GaAs and finds curves which agree well with those of Tauc and Abraha´m. His analysis of these results using the dispersion relation predicts a plasma energy near 7 ev in these materials. Free carrier absorption in several III–V compounds and in PbS and PbTe is proportional to &lgr;pat long wavelengths, wherepvaries between 2, for InSb and AlSb, and 3, for InAs and GaAs. Forn‐ andp‐type PbS Riedl findsp=2.4. He observes additional structure near the intrinsic absorption edge ofp‐type PbTe, resembling that observed inn‐type GaAs and GaP, which may be associated with a valence band about 0.1 ev below the band edge. The absorption coefficient near the absorption edge of all the lead compounds and of InAs is proportional toeℏ&ohgr;/kTeff, with 80°K<Teff<120°K for measurements taken at room temperature. Impurity effects on the energy gap are discussed in terms of a simple model.

ISSN:0021-8979    

DOI:10.1063/1.1777036

出版商:AIP    

年代:1961

数据来源: AIP