HETEROJUNCTION BIPOLAR-TRANSISTORS WITH EMITTER BARRIER LOWERED BY DELTA-DOPING

An Npn heterojunction bipolar transistor with a Si-delta-doped layer a t the emitter-base hetero-interface is demonstrated. The Si delta-dope d layer reduces the potential spike at the emitter junction. This desi gn reserves the abruptness of the heterojunction, reduces electron bar rier and increases the hole barrier simultaneously. Experimental resul ts show that the HBT's turn-on characteristics are greatly improved wh ile the current gain remains high. The offset voltages as low as 44 mV have been obtained. Very high current gains at very low collector cur rent densities are obtained.