Abstract: A large single crystal of metal orthophosphate is grown from a plurality of seed crystals by first mounting the seed crystals with one planar surface of each seed crystal substantially in contact with a planar surface of an adjoining seed crystal and a second planar surface substantially parallel to a second planar surface of the adjoining seed crystal. By known methods, the seeds are then grown into a large single crystal in an acid medium at elevated temperatures. The process is particularly useful for growing large crystals of berlinite, which can then be cut into wafers useful in surface acoustic wave devices.

Abstract: Large single crystals of berlinite are grown onto seed crystals by maintaining the crystals at a fixed elevated temperature in a pressure vessel containing a nutrient of coarse berlinite crystalline powder, held at a fixed lower temperature, and concentrated phosphoric acid. Because berlinite shows retrograde solubility, the nutrient goes into solution, and berlinite deposits on the higher-temperature growing crystal. The vessel is rocked to promote motion of saturated solution to the crystal and depleted solution to the nutrient. Large single crystals of alpha-gallium orthophosphate may be grown using the same apparatus and a similar process. The resultant crystals may be cut into wafers useful in surface acoustic wave devices.

Abstract: Berlinite crystalline powder of uniform particle size and high purity is prepared by repeated thermal cycling to react a mixture of aluminum hydroxide or aluminum oxide and an excess of concentrated phosphoric acid in a sealed pressure vessel. The vessel is preferably held in a horizontal orientation and rotated about a longitudinal axis during the reaction. The product powder is useful in growing large single crystals that have surface acoustic wave applications. Crystalline powder of alpha-gallium orthophosphate may be prepared using the same apparatus and a similar procedure.

Abstract: Large single crystals of berlinite are grown onto seed crystals by maintaining the crystals at a fixed elevated temperature in a pressure vessel containing a nutrient of coarse berlinite crystalline powder, held at a fixed lower temperature, and a mixture of hydrochloric and phosphoric acids. Because berlinite shows retrograde solubility in the acid mixture, the nutrient goes into solution, and berlinite deposits on the higher-temperature growing crystal. Large single crystals of alpha-gallium orthophosphate may be grown using the same apparatus and a similar process. The resultant crystals may be cut into wafers useful in surface acoustic wave devices.

Abstract: Large single crystals of berlinite are grown onto seed crystals by maintaining the crystals at a fixed elevated temperatutre in a pressure vessel containing a nutrient of coarse berlinite crystalline powder, held at a fixed lower temperature, and concentrated phosphoric acid. Because berlinite shows retrograde solubility, the nutrient goes into solution, and berlinite deposits on the higher-temperature growing crystal. The vessel is rocked to promote motion of saturated solution to the crystal and depleted solution to the nutrient. Large single crystals of alpha-gallium orthophoshate may be grown using the same apparatus and a similar process. The resultant crystals may be cut into wafers useful in surface acoustic wave devices.

Abstract: Berlinite crystalline powder of uniform particle size and high purity is prepared by repeated thermal cycling to react a mixture of aluminum hydroxide or aluminum oxide and an excess of concentrated phosphoric acid in a sealed pressure vessel. The vessel is preferably held in a horizontal orientation and rotated about a longitudinal axis during the reaction. The product powder is useful in growing large single crystals that have surface acoustic wave applications. Crystalline powder of alpha-gallium orthophosphate may be prepared using the same apparatus and a similar procedure.

Abstract: Heterodiodes showing excellent potential for use in solar cells and photoelectric devices consist of junctions of p-type indium phosphide and n-type cadmium sulfide. These heterojunctions can be formed either from single crystal or from polycrystalline semiconductor material. The former type junction when incorporated in a solar cell exhibits promise for applications such as in space vehicles. The latter type junction as used in a solar cell has potential for large scale power generation. A chemical vapor deposition process for producing polycrystalline p-type indium phosphide films for incorporation into such a power producing device is disclosed.

Abstract: A hydrogen transport process for cleaning the surface of an indium or gallium based semiconductor material and for depositing n-type cadmium sulfide on the cleaned semiconductor material is disclosed. The cleaning and deposition can be accomplished in sequence or simultaneously. The process entails adding hydrogen sulfide to a hydrogen gas flow in a chemical vapor deposition process. Single crystalline photovoltaic cells of p-InP/n-CdS with a 13.5% efficiency have been reproducibly fabricated. An efficiency of 4.6% has been obtained with a thin layer polycrystalline p-InP/n-CdS cell. Additionally, a p-GaAs/n-CdS heterodiode cell has been produced.

Abstract: Solar cells showing improved efficiency, amounting to about 14 percent for overall solar power conversion, are obtained by annealing InP/CdS solar cells in a slightly reducing atmosphere for about 15 minutes in a temperature range preferably from about 550.degree. centrigrade to about 600.degree. centigrade. In an annealing temperature range from 400.degree. centigrade to 625.degree. centigrade, an inversely dependent adjustment of annealing time is found desirable. The atmosphere preferably comprises mainly a substantially inert component and typically comprises an H.sub.2 + N.sub.2 mixture, such as forming gas (15% H.sub.2 + 85% N.sub.2).