| 摘要 |
PURPOSE:To provide a ballast function and to contrive the improvement of current amplification factor by controlling the concentration of emitter current by a method wherein a region forming a depletion layer by no bias is provided in each emitter layer in a transistor with multi-emitter structure or comb emitter structure. CONSTITUTION:A P type base layer 12 forming a P-N junction with an N type collector layer 11 is formed on the N type collector layer 11 and an N<+> type emitter layer 13 is formed on the surface of the P type base layer 12. An N<-> type layer 17 with low impurity density is provided in the emitter layer 13 to control current concentration. The surface of the N<-> type layer 17 and that of a base. emitter junction are covered with insulating films 18, 19. As a matter of fact, a plurality of the elements are formed in common with the collector and base for parallel operation. The current concentration control layer may be composed of P type layer 20 instead of the N type layer 17. In this way, with a ballast function provided in the elements, current distribution is equalized to expand the safety operation region of a transistor and current amplification factor is also increased. |
