DE1639146

1,213,017. Electroluminescence. WESTERN ELECTRIC CO. Inc. 15 Feb., 1968 [15 Feb., 1967], No. 7376/68. Heading C4S. [Also in Division H1] A semi-conductor device is produced by forming a P-type GaP crystal by solution growth, depositing an epitaxial layer of N-type GaP on the crystal, and annealing at a temperature between 450‹ and 725‹ C. The annealed device emits visible radiation (red) with an external quantum efficiency greater than 1%. In an example a quantity of gallium was heated in vacuo, specified quantities of gallium phosphide, zinc and gallium oxide were added and the tube was sealed under vacuum and heated to melt the solution which was then cooled. The resulting P-type GaP crystals was recovered by digestion in nitric acid. The crystal was polished and etched and placed at one end of a boat the other end of which contained a charge of gallium, gallium phosphide and tellurium. The boat was heated in a forming gas atmosphere to melt the charge which was then flooded over the crystal and allowed to cool to epitaxially deposit an N-type GaP layer on the seed crystal which was again recovered by digestion in nitric acid. The crystal was broken into two and annealed in air at 720‹ C. for 16 hours. As shown, Fig. 1C, ohmic contacts were applied to the P-type region 11 and the N-type region 12 by simultaneously alloying a gold zinc wire 16 and a tin dot 14 in a stream of hydrogen. The tin dot was contacted by a gold wire 15 and the device was mounted on a glass header 17 by means of a layer 18 of resin having a suitable refractive index. The external quantum efficiency was measured and found to be 2À1% compared with 0À26% for a device in which the annealing step was omitted. The annealing step may be performed at a temperature of 450‹ to 725‹ C. for 5 to 30 hours in an ambient of air, vacuum, or argon. The digestion of the GaP crystal from the gallium may also be performed with hydrochloric acid.