High-frequency power transistor with improved reverse-bias second breakdown characteristics

摘要

1,147,676. Semi-conductor devices. RADIO CORPORATION OF AMERICA. 4 July, 1966 [19 July, 1965], No. 29921/66. Heading H1K. The collector region 14 of a transistor 10 comprises at least three regions 20, 22, 24, the respective resistivities of which decrease in a step-wise manner in the direction away from the base region 16. The thicknesses of the two regions 22, 24 nearest to the base region 16 are substantially equal. As shown the region 20 is a degenerate N-type Si substrate on which are epitaxially deposited separate N-type layers 22, 24, the latter layer being of higher resistivity than the former. Alternatively the regions 22, 24 may be deposited epitaxially as a single layer, control of the N-type dopant, e.g. phosphorus pentoxide, during the deposition process providing the two distinct resistivity regions. The resistivity of the substrate 20 is preferably lower than that of the upper layer 24 by a factor of at least 100 : 1. The resistivity of each of the layers 20, 22 24 may vary slightly within the layer. The base region 16 is formed by P-type diffusion into the upper collector region 24, and the emitter region 18 is formed by heavily diffusing an N-type dopant into the base region 16. The invention may also apply to a PNP transistor, and Ge may replace Si.