TRANSPORT CHARACTERISTICS OF A SYMMETRICALLY EXTENDED BIPOLAR-TRANSISTOR

This work deals with a novel bipolar transistor structure consisting o f a deltap(B) - deltan(E) - deltap(B) planar doping layer sequence em bedded between two heavily doped n+ collector layers C and C. Current s flowing in such a n+ deltapdeltandeltapn+ structure are investigated under symmetrical bias conditions (V(EB) = V(EB), V(BC) = V(B*C*). A t V(EB) > 0 (forward bias), electrons, injected from the E layer over the B (B) barrier, are collected in the C (C*) layer whereas holes, i njected from B and B over the E barrier, are collected in the respect ive counter-layer B and B. In this structure, at V(BC) = 0, the diffe rence between the total current emitted from E and the current collect ed in C and C equals the electron-hole recombination current between E and B (E and B). Accordingly, the current gain depends linearly on the recombination lifetime in the E - B (E - B) region. At reasonable lifetimes (tau = 1 mus) appreciable current gain values are obtained even at high B (B) doping levels.