AVALANCHE MULTIPLICATION IN GAINP GAAS SINGLE-HETEROJUNCTION BIPOLAR-TRANSISTORS/

The electron multiplication factors in GaInP/GaAs single heterojunctio n bipolar transistors (HBT's) have been measured as a function of base -collector bias for a range of GaAs collector doping densities. In the lowest doped (5 x 10(14) cm(-3)) thick collector the multiplication i s determined by the local electric held, As the collector doping incre ases, the measured multiplication is found to be significantly reduced at low values of multiplication from that predicted by the electric f ield profile. However, good agreement is always found at high multipli cation, close to breakdown, This reduction in multiplication at low el ectric fields is attributed to the dead space, the minimum distance ov er which carriers must travel before gaining the ionization threshold energy, A simple correction for the dead space is proposed, allowing t he multiplication to be accurately predicted even in heavily doped str uctures.