| 摘要 |
1,017,355. Unipolar transistors. WESTING- HOUSE ELECTRIC CORPORATION. May 15, 1964 [May 29, 1963], No. 20310/64. Heading H1K. A silicon carbide unipolar transistor is produced by preparing a wafer consisting of an inner region of one conductivity type surrounded by an outer region of the opposite type, etching away parts of the outer region to expose sites in the inner region to which ohmic source and drain electrodes are applied and applying an ohmic contact or contacts to the outer region to serve as a gate electrode or electrodes. In Fig. 5 the source and drain electrodes are 66 and 68 and electrodes 70 and 72 are gates: in Fig. 6, 98, 100 and 102, 104 are the corresponding electrodes. The N-type inner region of the devices shown is nitrogen doped and the P-type outer region has been formed by a subsequent thermal diffusion of aluminium into the surface. The etching is performed electrolytically in a bath (Fig. 3, not shown) of HF in methyl alcohol, using the wafer as anode; under these conditions the outer P-region dissolves readily but the inner N-region does not. The electrodes may be of gold, tungsten, tantalum or alloys thereof which may be alloyed to the crystal, but are preferably of silicon which may be vapour deposited. As shown the electrodes are silicon, doped with phosphorus in the case of the connections to the N-region and boron for the P-region. Each electrode is capped by a silver foil contact, e.g. as at 78, Fig. 5.
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