Double-heterostructure GaAs–Alx Ga1−x As injection lasers which operate continuously at heat-sink temperatures as high as 311°K have been fabricated by liquid-phase epitaxy. Thresh-olds for square diodes as low as 100 A/cm2 and for Fabry-Perot diodes as low as 1600 A/cm2 have been obtained. Some details of preparation and properties are given.

We have succeeded for the first time in artificially tuning the conduction and valence-band barrier heights at an abrupt intrinsic semiconductor-semiconductor heterojunction via a doping interface dipole (DID). This is achieved by means of ultrathin ionized donor and acceptor sheets in situ grown within ≲100 Å from the heterointerface by molecular beam epitaxy. In the limit of a few atomic layers separation between the charge sheets this amounts to modify the effective band-edge discontinuities. A near one order of magnitude enhancement in the photocollection efficiency of an abrupt AlGaAs/GaAs heterojunction has been observed as result of the conduction-band barrier lowering induced by the DID.

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Using a tunable laser operating near 2 μm, second harmonic generation was observed in a GaAs waveguide having a grating etched in one interface. Phase matching occurs when β2−2β1−ϑ=0, where ϑ=2π/Λ is the wave vector of the grating of period Λ and β1 and β2 are the fundamental and harmonic wave vectors.

Small area silicon p-n junctions have been made which are free from exposed edges and dislocations passing through the space-charge region. It is believed that the space-charge regions of these junctions more closely resemble plane parallel geometries than any studied similarly hitherto. The avalanche breakdown phenomena in these uniform junctions are shown to be drastically different from those occuring in junctions that contain many dislocations. A comparison is made between the uniform junctions and one that is similar except that it possesses two breakdown-inducing sites, probably dislocations. In the latter junction the reverse characteristic shows two slightly separated rapid increases in current which coincide, biaswise, with the formation of two isolated light-emitting microplasmas, the occurrence of characteristic microplasma noise, and two singularities in the charge-multiplication characteristics. The uniform junctions show no such phenomena at intermediate voltages, breakdown occurring at a voltage roughly twice that at which the microplasmas form and which was previously thought typical for the given material resistivity. The light emission pattern accompanying breakdown in the uniform junctions appears more diffuse (giving rise to the term—macroplasma) than in nonuniform junctions where it normally appears as an array of intense local spots (microplasmas). It is concluded that microplasmas are not a necessary accompaniment of avalanche breakdown in silicon, but that they tend to occur where there are field or lattice inhomogeneities.