METHOD OF PRODUCING SEMICONDUCTOR BODIES

摘要

1293408 Making semi-conductor lasers WESTERN ELECTRIC CO Inc 22 Dec 1969 [23 Dec 1968] 62286/69 Heading H1K A laser structure is produced by growing an epitaxial layer of zinc-doped gallium aluminium arsenide on an N-type gallium arsenide substrate, zinc being diffused from the layer into the substrate to form a PN junction during and/or after the growth of the layer. Evaporated contacts respectively of gold and tin are formed on the lapped layer and substrate, and the structure is then cut and cleaved to form individual diodes. The arsenide layer is grown from a source solution of gallium arsenide, aluminium, and zinc in gallium and having an aluminium content of greater than 0À05 atom per cent and a zinc content in the range 0À1-1À0 atom per cent. The gallium arsenide is dissolved in the gallium under a hydrogen atmosphere and the cooled material placed with the aluminium and zinc in he well 16 of a carbon boat 14 in a quartz vesselt 11. After flushing with nitrogen, hydrogen is passed through the apparatus during the remainder of the process. The components of the source solution are heated to an initial temperature in the range 700-1100‹ C. to produce a melt which projects slightly from the well 16. The melt is cooled in a controlled manner to a predetermined temperature at which the furnace 22 is tilted so that sliding mass 17 impacts the remote end of the substrate carrier 15 which is thus moved to deposit an N-type gallium arsenide wafer 25 (lapped and etch-polished and having a carrier density of 3.1018-1À1019 electrons cm.-3) on the melt in the well, oxide scum &c. being cleared from the melt by the passage of carrier edge 19. Controlled cooling is continued and may include an annealing stage to extend zinc diffusion and modify the zinc concentration profile. A separate annealing stage may be carried out by reheating after the structure has been cooled to room temperature. Annealing (at any stage) may be carried out for more than an hour at a temperature in the range 800-1000‹ C. The furnace includes an observation window 23 and thermocouple 21 for monitoring. In a particular example the substrate 25 is GaAs with (111) major faces doped with Sn to an electron concentration of 4À2.1018 electrons cm.-3 and lapped and polished with bromine/ methanol. The source solution (specified) is heated to 1040‹ C. and the substrate dropped on, cooling being carried out at 5‹ C. per minute to 900‹ C. at which point the furnace is reverse tilted to remove the substrate from the source solution. The temperature is then held at 900‹ C. for 3 hours and then lowered to room temperature by removing the apparatus from the furnace. The PN junction-which should be within a minority carrier diffusion length from the hetero junction-is in this example 1À6 Á therefrom.