Diode semi-conductrice.

摘要

922,617. Semi-conductor devices. WESTERN ELECTRIC CO. Inc. Aug. 4, 1959 [Aug. 13, 1958], No. 26560/59. Class 37. In a semi-conductor device comprising a monocrystalline silicon body having N- and P-type regions separated by a planar PN junction the P and N regions are substantially uniformly doped with gold or platinum to reduce the minority carrier lifetime therein and hence the reverse recovery time of the junction. In one embodiment boron is diffused into both faces of an N- type silicon slice by heating in a boron containing gas, or by precoating with a solution of boricanhydride in ethylene glycol monomethyl ether and heating in air to 1230‹ C. for 16 hours. After removing one of the P-type layers thus formed the exposed N-type surface is coated with a solution of phosphorus pentoxide and heated for 2 hours at 1100‹ C. in air. Subsequently both faces are coated with gold and the slice heated in nitrogen at 1100‹ C. for an hour to effect complete solid solubility of the gold throughout the body. The concentration of gold is determined by the solid solubility and hence by the temperature of the diffusion. The P-type layer is largely removed ultrasonically to leave isolated islands of P-type and the plate cut ultrasonically into circular discs each including one such island (Fig. 2). Gold electrodes are finally plated on the P- and lower N-type surfaces of the discs to form diodes which may be encapsulated in known manner as shown in Fig. 3. In an alternative method both faces of the slice are first coated with gold, and boron and phosphorus containing layers applied over the gold on the upper and lower surfaces respectively. The slice is then heated in inert gas for 12 hours at 1250‹ C. to distribute the gold simultaneously and provide the PN junction. The preferred concentration of gold in the finished devices is from 1015 to 1017 atoms/cc. Specifications 782,662, 809,644 and U.S.A. Specification 2,758,787 are referred to.