| 摘要 |
951,103. Transistors. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. June 10, 1960 [June 23, 1959], No. 21497/59. Heading H1K. A unipolar transistor is made from partially compensated semi-conductor material containing donors and acceptors, in the form of two monocrystals separated by a grain boundary or a monocrystal containing a line of dislocation, by the following steps. The semi-conductor is heated to diffuse the dominant impurity preferentially towards the line of dislocation or grain boundary where it reacts with another impurity to form a stable complex and thus becomes ineffective as an activator. As a result the immediately surrounding region in which the other impurity becomes dominant forms a PN junction with the main body. Ohmic contacts are made to the ends of this region and at least one contact to the main body to complete the transistor. In an embodiment the basic semiconductor material is P-type silicon containing phosphorus and aluminium as impurities. The material is grown from a suitably doped melt in a quartz crucible to ensure an adequate supply of oxygen in the silicon. When the body is heated to 1200-1250‹ C. in an evacuated or inert gas filled quartz container aluminium diffuses to the surface and to the dislocation and there forms a complex with oxygen. After the heating there is more phosphorus than aluminium in the regions adjacent the surface and grain boundary or dislocation which are therefore N-type. The N-type surface is ground off and the profile of the PN junction about the dislocation revealed by preferential etching of the P zone in specified acid etches. Ohmic contacts of gold antimony are then provided at the ends of the N region and aluminium contacts on the P region. The initial proportions of aluminium and phosphorus in the starting crystal are so adjusted that the aluminium depleted region formed about the dislocation or grain boundary is of higher resistivity than the rest of the body. The final zone configurations resulting from using a planar grain boundary and line dislocation respectively are shown in Figs. 2 and 3, respectively. Specifications 936,831, 936,832 and 936,833 are referred to.
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