Patent GB-1008743-A (GB)
Title: Modulating energy flowing in semiconductors
IPC: G02F1/015
Filed: 1963-10-07
Abstract: 1,008,743. Semi-conductor devices. INTERNATIONAL BUSINESS MACHINES CORPORATION. Oct. 7, 1963 [Oct. 30, 1962], No. 39367/63. Heading H1K. [Also in Division H4] The invention comprises modulating electromagnetic radiation by selectively stressing elastically a semi-conductor element through which it is propagating, in particular modulating recombination radiation emanating from a P-N junction in a semi-conductor element by selectively stressing elastically an adjacent region through which it is propagating. In Fig. 1, a semi-conductor element 10 surrounded by fluid 14 in a chamber 12 is uniformly stressed by force F on piston 17, the stress being illustrated as stress vectors S. Electro-magnetic radiation 20 with quanta 22 is propagated into surface 24 and by selectively applying the stress S modulated electromagnetic radiation 26 having quanta 28 propagates from surface 30. In a forward biased semi-conductor element recombination radiation, i.e. light 58, is generated at P-N junction 55 (Fig. 6) and modulated by applying elastic stress S to N-type region 54. In an electro-optical transistor, Fig. 8, recombination radiation 76 emanating from P-N junction 70 causes electron-hole pairs at N-P junction 71 and by application of elastic stress S the radiation is modulated and the collector current flowing in load resistor 74 indicated by meter 73 is also modulated. Junction 71 is either a heterojunction or a homojunction. The immediate environment of junction 71 may be doped to cause a built-in field to separate electron-hole pairs generated by absorption of photons, thus facilitating the modulation of the output radiation. Electromagnetic radiation propagated into an acoustic-optical transducer (Fig. 9, not shown) is modulated by applying acoustic energy to the semi-conductor, thus producing elastic deformation. The effect of stress is different dependent upon whether the semi-conductor is class A, e.g. aluminiumantimonide, and gallium-phosphide, or class B e.g. gallium-arsenide and germanium. When stress is applied the width of the forbidden band becomes smaller for class A and larger for class B and when the width of the forbidden band is below a " threshold width" no radiation is propagated and when it is above a " maximum width " all the radiation is propagated. When the incoming radiation 20 (Fig. 1) is monochromatic and when the forbidden band width is made smaller, the output radiation remains monochromatic but has a smaller intensity amplitude and when it is polychromatic and the forbidden band width is made smaller, higher frequencies are absorbed in addition to the intensity being reduced. Further, in a class A semi-conductor stress applied to a P-N junction causes the recombination radiation resultant from stimulated emission to have a longer wavelength and in a class B to have a shorter wavelength. Impurity elements in a class B semi-conductor permits more radiation to propagate through when stress is applied since recombination transitions may occur between a donor level and an acceptor level. Absorption of the radiation by radiationless transitions occur when the semi-conductors incorporate doping elements. The temperature of fluid 14 (Fig. 1) is controlled so that the temperature of the stressed region is constant.