The phonon spectra of Ga1−xInxAs have been studied by measuring the infrared reflectivity at near-normal incidence in the 180 ∼400-cm−1 frequency range. Only one reststrahlen band corresponding to the GaAs-like mode was observed for x≲0.2, and two bands were observed for the remaining composition. The data were analyzed by using the Kramers-Kronig relationship and the dependence of the mode frequencies on alloy composition was interpreted on the basis of the modified cluster model including the effect of clusters. The fact that the calculated oscillator strength for the InAs-like mode is substantially zero in the composition range x≲0.2 explains the reason why phonons of the InAs-like mode are not detected experimentally for x≲0.2. The clustering parameter representing the effect of clusters is determined by fitting the measured mode frequencies to the calculated compositional dependence and takes the maximum value near the midrange of alloy composition.

Raman scattering, electron diffraction, and dark-conductivity measurements have been made on so-called a-Si films deposited at various rf powers by a glow-discharge technique. These measurements show that an abrupt transition between amorphous and polycrystalline states occurred between 350 and 370 rf voltages and films deposited at high rf voltages are polycrystalline. Dark conductivity of the silicon films changed largely with the amorphous-to-crystalline transition. It is also observed that some polycrystallized silicon films exhibited new peaks between 505 and 513 cm−1 in the Raman spectra.

A simple method is proposed to determine the series resistance R s and the perfection factor n of solar cells from the measurement of the tangents to the current I–voltage V curve at constant light intensity. The values of R s and n thus determined are then used to predict the maximum power P m and the voltage V m at which the power gets maximum. This new method is applied successfully to the conventional cell, BSF (Back Surface Field) cell and the textured BSF Si cell. A good agreement is obtained between the calculated- and the directly measured values of V m and P m.