Paul M. Raccah

Variations in composition in binary and ternary semiconductors utilizing electrolyte electroreflectance: A topographical investigation

Utilizing electrolyte electroreflectance, we have developed a unique approach for determining the variations in composition x across the face of binary and ternary alloy semiconductors. This technique is based on the fact that the energies of features in the optical spectra of semiconducting alloys depend on x in a continuous manner. Any shift in energy of a particular electroreflectance peak is measured using a small scanned light spot. Corresponding variations in x can be determined to within about 1% with a spatial resolution of about 100 μm. This technique is nondestructive and can readily be employed under atmospheric conditions at room temperature. Results are presented for a number of alloys, including Hg1−xCdxTe, Ga1−xAlxAs, InAsxSb1−x, and Pb1−xSnxTe. The advantages of our approach in relation to microprobe or luminescence methods is discussed.

Crystal growth and study of the stoichiometry of NbO2

Abstract Large NbO 2 single crystals of controlled stoichiometry have been prepared by the Czochralski-Kyropoulos technique in a tri-arc furnace. A study of the stoichiometry shows that the compositional range of existence extends much further than was previously reported and that the conductivity depends on composition also in contrast with earlier work.

Current controlled liquid phase epitaxial growth of Hgl−xCdxTe

Using the technique of current controlled liquid phase epitaxy we have grown crystalline layers of Hgl-xCdxTe from a Hg-melt. Best results were obtained on (111) oriented substrates. The dominant mechanism of solute transport is electromigration rather than the Peltier effect. Composition (x ≈0.1) and homogeneity across a sample surface (Δ x ≈ 0.03) was determined by the electrolyte electroreflectance method.

Variations in the carrier concentration in elemental and compound semiconductors utilizing electrolyte electroreflectance: A topographical investigation

Utilizing electrolyte electroreflectance we have developed a convenient nondestructive room‐temperature technique for evaluating the topographical features of the variations in the carrier concentration across the surface of semiconductors with a spatial resolution of about 100 μm. We report measurements on several element and compound semiconductors including silicon, germanium, GaAs, and InSb. The advantages of this method in relation to other techniques will be discussed.

Resonance Raman scattering in Ti2O3 in the range 1.8–2.7 eV

Abstract Measurements of resonance Raman scattering from the A 1 g and E g modes of Ti 2 O 3 at room temperature were made in the energy range 1.8–2.7 eV. The results are interpreted in terms of a phonon modulation of the optical spectrum and related energy level structure. New information concerning assignments of interband transitions as well as further insight into the nature of d -electron/phonon interaction has been obtained.

Variations in stoichiometry in Hg 1− xCdxTe using electrolyte electroreflectance: a topographical investigation

We have developed a unique approach for evaluating the local composition x as a function of position on the surface of crystals of Hg(1-x) Cd(x) Te utilizing electrolyte electroreflectance. The method is nondestructive and can be employed at room temperature. The technique is sensitive enough to determine changes of composition Deltax approximately 0.002 for samples in which x approximately 0.2-0.3 with a spatial resolution of about 150 microm. This approach has a number of advantages over the microprobe technique.

Piezo-modulated spectroscopic investigation of N and N-N Pairs in GaP

SummaryWe have investigated the effects of uniaxial compression along [001], [111] and [110] on the modulated-transmission spectra of an exciton bound to an isolated N as well as to N-N pairs. Our results show that the observed stress-induced splittings are associated with the valence band splitting, suggest that internal-strain effects may be significant for N and N-N pairs, and that the N-N pair interaction in weak.RiassuntoSi sono analizzati gli effetti della compressione uniassiale lungo le direzioni [001], [111], [110] sugli spettri di trasmissione modulata di un eccitone legato a un N isolato o anche a coppie N-N. I nostri risultati mostrano che le separazioni indotte dallo sforzo che si osservano sono associate a separazioni della banda di valenza, suggeriscono che effetti di tensione interna possono essere rilevanti per N e per coppie N-N e che l’interazione tra coppie N-N è debole.РезюмеМы исследуем влияние неаксиального сжатия вдоль [001], [111] и [110] на модулированные трансмиссионные спектры экситона, связанного с изолированным N, а также с N-N парами. Наши результаты показывают, что наблюденные расщепления, индуцированные напряжением, связаны с расщеплением валентной зоны. Предполатается, что влияние внутренних напряжений может быть существенным для N и N-N пар и что взаимодействие N-N пар является слабым.