| 摘要 |
1,263,485. Semi-conductor devices. MATSUSHITA ELECTRIC INDUSTRIAL CO. Ltd. 23 June, 1969 [19 July, 1968; 20 Sept., 1968], No. 31589/69. Heading HIK. An oscillator device comprises a semiconductor body 10 including two regions 11, 12 of the same conductivity type, the lower conductivity region 11 itself including a breakdown region in which the minority carrier lifetime exceeds and in which the carrier concentration is less than half the corresponding values in the remainder of the body 10. This may be achieved by providing a zone close to the surface of the region 11 where the majority carrier concentration, determined by the donor concentration in the embodiment shown, is lower than in the rest of the region 11, as shown schematically in Fig. 6. Oscillations whose frequency depends upon the applied voltage result from repeated avalanche breakdowns in the long lifetime region where the highest field strength occurs, followed by minority charge storage adjacent the surface of the region 11 thus reducing the maximum field strength and causing breakdown to cease, and recombination of the stored carriers with further majority carriers allowing the field strength in the breakdown region to increase once again to the breakdown value. The body 10 may be of Si, Ge or GaAs and the lower conductivity region 11 may be formed epitaxially on an N + substrate, the donor content being varied during growth of the region 11 to provide the necessary low concentration breakdown region. Alternatively the entire body 10 may initially be heavily doped and may be immersed in a solution including a dopant which will reduce the carrier concentration close to the surface of the body. The solution may be FeCl 3 for Fe dopant, CuSO 4 for Cu dopant or NiCl 4 for Ni dopant. |
