Single-crystalline, colorless, GaN has been prepared by a vapor-phase growth technique previously used to prepare GaAs, GaP, and GaSb. These crystals are the first reported speciments of GaN suitable for good electrical and optical evaluation of this compound. It has been determined that GaN has a direct energy bandgap of 3.39 eV, and that undoped crystals prepared by this method have a very high inherent electron concentration, typically above 1019/cm3, which is probably related to a high density of nitrogen vacancies. Conducting p-type specimens have been prepared using Ge as the dopant; but this result has been difficult to reproduce, and the samples have been electrically inhomogeneous.

Single crystal GaAs1−xPx layers have been grown epitaxially from the vapor phase in a novel apparatus, using gaseous arsine and phosphine as sources of arsenic and phosphorus. These layers exhibit the highest quality, and the widest range of controlled resistivity yet reported for solid solutions in this system. Vegard's law is obeyed over the entire composition range. At room temperature, the change from a direct to an indirect transition across the band gap occurs at the value, x=0.44 . Electron mobilities in these layers are high; a sample containing 27% normalGaP , for instance, had a room temperature mobility of 4900 cm2/v‐sec, and a 69% gallium phosphide alloy had a mobility of 700 cm2/v‐sec at room temperature. Both n‐ and p‐type doping have been obtained, with hydrogen selenide gas and zinc vapor as the sources of donor and acceptor impurities, respectively. In this apparatus it is also easy to prepare multilayered structures incorporating layers of different resistivity and/or composition.

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A series of GaAs1−xPx diodes have been prepared by a vapor‐phase growth technique to investigate the effects of current‐spreading, absorption, impurity concentrations, and alloy composition on room‐temperature electro‐luminescent efficiencies. It is shown that for maximum efficiencies, a diode structure should be prepared with a p+ surface layer to enhance current spreading, and a GaAs1−xPx “window” containing about 10% more normalGaP than the p‐n junction region to reduce absorption losses. It is also shown that the most efficient radiative recombination originates on the p‐side of the junction; low acceptor concentrations and high donor concentrations which are required for strong electron injection into the p‐side of the junction are thus found to result in highest electroluminescent efficiencies. Slow compositional grading between the normalGaAs substrate and the GaAs1−xPx p‐n junction also resulted in increased efficiencies. A drop‐off in efficiency near the direct‐indirect transition for values of x increasing from 0.38 was found to be severe, however, a corresponding increase in the spectral sensitivity of the eye was found to provide a broad maximum in diode brightness at emission wave‐lengths near 6800Aå ( x≈0.38 ). Planar uncoated diodes have provided brightness values in excess of 300 ft‐L at 10 amp/cm2 with external efficiencies of 2×10−4 at 6400Aå. Plastic encapsulants ean be readily used as domes to increase external efficiencies by a factor of 3, or as directional lenses to provide beam‐widths as narrow as 7°.

Heteroepitaxial InP layers grown by metalorganic chemical vapor deposition on novel GaAs on Si buffers obtained by molecular beam epitaxyStructural and optoelectronic properties and their relationship with strain relaxation in heteroepitaxial InP layers grown on GaAs substrates