The influence of uniaxial stress in 〈111〉 direction on the free carrier contribution to the optical constants of multivalley semiconductors is considered according to the electron transfer model. Calculations are made of the resulting change in absorption and shift of the wavelength for minimum reflection. It is shown that these effects may be large and experimental observation of them provides a method of determining the effective mass and relaxation time parameters and their anisotropies. The possibility of constructing infrared modulators based on these phenomena is also examined.



Es wird der Einflus des Druckes in 〈111〉-Richtung auf den Beitrag freier Ladungs-tragern zu den optischen Konstanten von Vieltal-Halbleitern entsprechend dem Modell der Elektronenstreuung untersucht. Rechnungen werden fur die sich ergebenden Anderungen der Absorption und Wellenlange fur minimale Reflexion durchgefuhrt. Es wird gezeigt, das diese Effekte betrachtlich sein konnen; ihre experimentelle Beobachtung bietet eine Methode, die effektive Masse und Relaxationszeit, sowie ihre Anisotropien zu bestimmen. Die Moglichkeit, Infrarot-Modulatoren herzustellen, die auf diesen Prinzipien beruhen, wird ebenfalls untersucht.

Infrared Modulation and Energy Band Parameters in Multivalley Semiconductors through Uniaxial Stress Dependence of Free Carrier Contribution to Optical Constants

The production of highly perfect crystals is of considerable scientific and technical importance, and there has been increasing interest in methods of examining crystal perfection. X-ray topographic methods provide abundant information on lattice defects of various scales. A major area of development in recent years has been the determination of crystal perfection by the direct observation of growth defects. X-ray topography here has considerable advantages over electron microscopy and optical methods. The sensitivity is high, while it is possible to examine the bulk distribution of various kinds of defects in comparatively large specimens. Here we consider methods that allow one to examine macroscopic defects (block structure) and microscopic ones (dislocations, inhomogeneous impurity distributions, inclusions, and so on), and results are given from these methods applied to crystals grown under various conditions.

X-ray Diffraction Topography of Growth Defects in Crystals

The operation of fused‐silica Debye‐Sears light modulators is investigated for normal light incidence over a range of conditions such that the effect of amplitude modulation of the light beam by the acoustic wave, as well as phase modulation, must be taken into account. Using the approximations of Raman and Nath, for which the ultrasonic wave can be treated as a phase grating, the relationships between input electrical excitation and the resulting spatial modulation are determined for shear and compression waves. The effect of the length of the light path on the operation of the light modulator is then considered for a range of values for which Raman and Nath's simplified approach is no longer valid. From the results of Bhatia and Noble it is shown theoretically and verified experimentally that, for single frequency excitation, a value of this dimension can be specified such that the effective spatial modulation of the light beam can be maximized. The case of electrical excitation over a finite frequency ...

L. B. Lambert

Papers

Transfer Characteristics and Frequency Response of Wide‐Band Amorphous‐Solid Debye‐Sears Light Modulators