| 摘要 |
828,023. Semi-conductor elements. GENERAL ELECTRIC CO. Aug. 15, 1957 [Aug. 16, 1956], No. 25783/57. Class 37. A junction transistor is produced by melting back and refreezing a portion of a semi-conductor body containing an impurity, so as to form a region of low impurity concentration at the solid liquid interface, and then heating to diffuse an impurity characteristic of the opposite type so that it predominates in this region. The body may initially contain both the donor and acceptor impurities. Fig. 2 shows the resultant impurity concentration along a bar of Si using Sb and Ga as impurities. Originally (Fig. 2 (A)) the Sb concentration exceeds the Ga, so that the bar is N-type throughout. After melt-back, the segregation coefficients being less than unity, the concentration of both Sb and Ga is reduced near the interface but Sb remains predominant, while the concentration of both increase in the recrystallized portion away from the interface. The rod is now heated to about 1200‹ C. for two hours which causes the Ga (which diffuses faster than Sb in Si) to become predominant in the region adjacent the interface, as shown in Fig. 2 (C), to provide an NPN structure. Ge may be used instead of Si and Sb.In; Sb.B; Sb.A1; Ga.As; P.A1 ; P.Ga; As.B; As.In; As.A1; and In.Pare specified as alternative impurity combinations. By choosing impurities such as As and B in Si and freezing slowly, and then quickly after the melting back, it is possible to arrange for the concentrations in the first recrystallized portion to be substantially equal, as shown in Fig. 3B. Subsequent diffusion of the B then provides an NPIN structure, as shown in Figs. 3C and 3D. Further embodiments are described using three impurities, such as In and Ga as acceptors and Sb as the donor, in Ge. In these cases, the In originally predominates, while Ga predominates after melt back and recrystallization. Subsequent diffusion of the Sb converts the interface region to opposite type conductivity as in the previous examples to provide a PNP structure. The use of the two acceptors enables separate control of the final resistivity of the two P regions which serve as emitter and collector, to be established. Other combinations of impurities given for use with Ge are In, Ga, As and In, Ga, P, and for use with Si are Sb, As, Ga; P, Sb, Ga; As, Sb, Al and P, Sb, Al. In a similar manner, silicon NPIN structures can be produced by using Sb, Ga, B or Sb, Ga, An. In a further embodiment (Fig. 7), a Ge pellet comprising only one impurity, Sb, is melted back to provide a concentration as shown in Fig. 7 (A). The pellet is then coated with Cu and heated at 800‹ C. for two hours to diffuse the Cu throughout the whole pellet, as shown in Fig. 7B, to provide an NPN structure. As and Ga may alternatively be used in Ge, or Al and As in Si for the same purpose.
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