J.B. Renucci

Characterization of implantation and annealing of Zn‐implanted InP by Raman spectrometry

First‐ and second‐order Raman scattering by Zn‐implanted InP is investigated in order to determine critical fluences needed for a complete disturbance of the lattice and recovery temperature during thermal annealing. Disorder‐activated first‐order acoustical scattering and second‐order optical scattering are shown to be highly sensitive probes.

Disorder activated Raman scattering in Ga1−xAlxAs alloys

Abstract We report Raman scattering experiments in mixed crystals Ga1−xAlxAs in the spectral range 20 – 400 cm−1. We performed the measurements for several incident and scattered light polarizations. Besides the D.A.L.A. already observed1 we find a new band at lower energy. We interpret this structure as due to disorder activated transverse acoustical phonons and label it D.A.T.A. Several weaker bands corresponding to disorder activated optical processes are also seen. Our results are compared with recent calculations of Talwar et al2.

RAMAN CHARACTERIZATION OF TWINNING IN HETEROEPITAXIAL SEMICONDUCTOR LAYERS - GAAS/(CA,SR)F2

Detailed analysis of Raman spectra recorded from (100)‐oriented GaAs layers grown by molecular‐beam epitaxy on the lattice‐matched insulator (Ca,Sr)F2 gives evidence of internal misorientation effects (twins). This analysis accounts for the various phenomena (doping, disorder, electron‐phonon coupling) likely to modify the scattering efficiency. Calculations are performed in order to obtain quantitative evaluations of the misoriented volume amount.

A new experimental method for the determination of the one phonon density of states in GaAs

Abstract The one phonon density of states in GaAs is obtained from the measured disorder-activated-first-order Raman-scattering in Ga 1− x Al x As x alloys. The agreement with several theoretical determinations is excellent. We discuss the requirements that, both the isoelectronic substitution and the experimental conditions must fullfil in order to apply this method to other III–V compounds.

Raman determination of the composition in semiconductor ternary solid solutions

The use of Raman spectrometry for the precise determination of the mole fraction in semiconductor solid solutions is presented. It is shown that if the frequency difference between the modes related to the two binaries involved is used, the scattering of the results due to various experimental conditions (temperature, spectrometer calibration, ...) is avoided. In addition, the method is rapid, nondestructive, reliable, and allows to probe the composition at different depths into the layer.

BOND RELAXATION PHENOMENON AND IMPURITY MODES FREQUENCIES IN III-V-COMPOUNDS

Abstract In regard with very recent studies which evidence the bond relaxation phenomenon in III–V solid solutions, a new approach is proposed to determine theoretically the isoelectronic impurity modes frequencies. It is based on an embedded molecular unit model which accounts for the relaxation in the neighboring of the substituted atom and so avoids both the single-site and virtual crystal approximations. The results obtained for GaAs in some III–V compounds are compared with the experimental available data.

Correlation between k = 0 optical phonons in NbS3 and phonons in ZrS3

Abstract We have investigated by Raman spectroscopy the long wavelength optical phonons of NbS 3 at 300 and 80 K. We have detected 20 phonons among the 24 k = 0 Raman active modes predicted by group theory. The Raman spectra exhibit a remarkable similarity with the analogous spectra of ZrS 3 . This may be understood from the close relationship between the structures of the two compounds. We could relate most of the k = 0 phonons in NbS 3 to zone center and zone edge phonons of ZrS 3 in the b ∗ direction. The occurrence of doublets may be explained by the flatness of the optical branches of the dispersion curves along the b ∗ -reciprocal axis of ZrS 3 , deduced from second order Raman measurements.

Selective resonant enhancement of disorder-activated phonons in Ga1−xAlxAs alloys

SummaryWe present resonant Raman experiments on first-order disorder-activated bands in Ga1−xAlxAs alloys. Selective enhancements occur, in particular, in the acoustic region. These resonances enable us to assign unambiguously the features revealed and to determine their mode behaviour. The enhanced disorder-activated bands are compared with the structures appearing in the Raman spectra of GaAs-AlAs superlattices.RiassuntoSi presentano esperimenti di Raman risonanti su bande di primo ordine attivate dal disordine in leghe Ga1−xAlxAs. Aumenti selectivi avvengono in particolare nella regione acustica. Queste risonanze permettono di assegnare in modo non ambiguo le caratteristiche rivelate e di determinare il loro comportamento di modo. Le bande aumentate attivate dal disordine sono confrontate con le strutture che compaiono negli spettri di Raman dei superreticoli di GaAs-AlAs.РезюмеМы предлагаем резонансные Рамановские зксперименты на неупорядоченных возбужденных зонах первого порядка в сплавах Ga1−xAlxAs. В частности, селективные усиления имеют место в акустической области. Зти резонансы дают возможностъ однозначно овъяснить овнаруженные особенности и определить поведение мод. Усиленные неупорядоченные возбужденные зоны сравниваются со структурами, возникаюЩими в Рамановских спектрах суперрешеток GaAs-AlAs.