Semiconductor Devices Including an n-Type Gallium Arsenide Substrate and Methods of Making Ohmic Contacts thereto

摘要

1,191,145. Semi-conductor devices. WESTERN ELECTRIC CO. Inc. 7 June, 1967 [8 June, 1966], No. 26187/67. Heading H1K. An N-type GaAs body 21 having a net donor concentration of 10SP16/SP atoms/c.c. or less has an ohmic contact applied thereto comprising an NSP++/SP layer 22 of GaAs having a net donor concentration of the order of 10SP20/SP atoms/c.c., with a metal layer 23 thereon. The body 21 may itself be epitaxially grown on an NSP+/SP GaAs substrate. The preferred method of applying the contact comprises growing the N ++ layer 22 epitaxially from a solution of tin saturated with GaAs (6-10 mole per cent GaAs) produced by melting together a mixture of tin and crushed N-type GaAs, by causing the solution to flow over the cleaned and etched N-type body 21 in a hydrogen atmosphere at 600‹ C., and then cooling. When the temperature reaches 500‹ C. the tin solution is decanted from the body 21 and further cooling takes place in nitrogen. Excess tin/GaAs is removed by heating the body under mercury covered with dil. HCl. The metal layer 23, which may consist of an In/Au alloy, is then formed, e.g. by evaporating In and Au on to the surface of the NSP++/SP layer, and heating so as to alloy them. A tiltable sealed furnace is described for carrying out the epitaxial growth of the NSP++/SP layer 22. This growth may take place through a mask on to a limited region of the body 21.