A very high sensitivity phototransistor structure

Nonhomogeneous base Bipolar Phototransistor (BPT) and Static Induction Phototransistor (SIPT) current amplification mechanisms are discussed, and comparisons are drawn to the features of homogeneous and graded base BPTs. The nonhomogeneously doped BPT's current transport mechanism is similar to that of the SIPT for the case of p(n) base potential that is capacitively controllable by both the p(-) (n/+/) base and collector voltages. For the n-channel SIPT in the open gate mode, the potential barrier height for holes stored in the p(+) gate region is higher than for electrons in the n(+) source region. An experimental and theoretical consideration of the steady-state and transient optical response of the SIPT in open gate operation is made. If a homogeneous BPT's base region is replaced by a nonhomogeneous base structure and/or static induction transistor gate structure, sensitivity and response time characteristics will be significantly improved. A static induction transistor converter employing such high senstivity SIPTs is proposed.