GB841193A - Improvements relating to the manufacture of p-n junction devices - Google Patents

Abstract

841,193. Semi-conductor devices. GENERAL ELECTRIC CO. June 14, 1956, No. 18423/56. Addition to 752,457. Class 37. In a method of forming a PN junction as claimed in the parent Specification, in which a portion of a semi-conductor body containing both a donor and an acceptor, is melted, the semi-conductor material is germanium or silicon, the donors and acceptors consist of B, Al, Ga, Jn, P, As or Sb and the concentration of each of these impurities in the melt from which the Ge or Si crystal is grown lies within a specified range. The ranges are as follows : 0À001-1 Á gm. B; 0À6 Ágm.-6 mgm. Al; 1À4 Ágm.-14 mgm. Ga; 200 Ágm.-20 gm. In; 0À26 Ágm.-2 mgm. P; 1À8 Ágm-50 mgm. As ; 40 Ágm.-13 gm. Sb in 100 gms. of Ee or À34 Ágm.-5 mgm. B; 360Ágm.-20 gm. Al; 370 Ágm.-20 gm. Ga; 8 mg.-20 gm. In; 5À6 Ágm.-140 mg. P ; 7À6 Ágm.-110 mg. As; 48 Ágm.-2À7 gm. Sb per 100 gms. of Si. To form a PN junction, the weight ratio of one activator to the other must lie between the ratio of their atomic weights times the inverted ratios of their segregation coefficients and the atomic weight ratio times the square of the inverted segregation coefficient ratio. Combinations of donors and acceptors which may be used to provide a weak re-crystallised N-region on a strong P-type body are P-Al; P-Ga; Sb-In; and In-As ; in Ge and P-Al; P-Ga; P-In; As-Al ; As-Ga ; As-In ; Sb-Al; Sb-Ga; and Sb-In in Si. Combinations to produce a weak re-crystallised P-resin on a strong N-type body are B-P; B-As ; B-Sb ; Al-As; Ga-As ; and Ga-Sb in Ge. The relative change in segregation coefficients with change in crystal growth rate may be used to provide two PN junctions in the body. Fig. 2 shows an N-type Ge body containing Sb and Ga, in which the top portion was melted and recrystallised, the first recrystallised region being P-type and then, due to the increase in crystal growth rate, the next portion to recrystallise was of N-type conductivity. This effect may also be obtained by using B-As; B-Sb; or B-P in Ge or S or Al-Sb, Al-As, Ga-Sb in Ge. For the two PN junction embodiments, the weight ratio of donor to acceptor in the melt preferably lies between 0À5 and 1 À times the atomic weight ratio times the square of the inverted segration coefficient ratio. The invention is applicable to diodes and transistors and reference is made to the use of nickel, aluminium and gold-antimony electrodes. Specification 738,231 is referred to. Reference has been directed by the Comptroller to Specification 781,795.