EMITTER MATERIAL COMPARISON BETWEEN INGAP AND INGAASP IN GAAS-BASED HETEROJUNCTION BIPOLAR-TRANSISTORS

In0.49Ga0.51P (E(g) = 1.87 eV)/GaAs and In0.38Ga0.62AS0.22P0.78 (E(g) = 1.77 eV)/GaAs Npn heterojunction bipolar transistors (HBTs) were fab ricated. In devices with 110 mum x 110 mum emitter areas, the curtent gains of both devices were the same value of 14 at a collector current density of 700 A/cm2. By contrast, the turn-on voltage of InGaAsP/GaA s HBTs was 0.01 V smaller than that of InGaP/GaAs HBTs, which indicate d that the conduction band discontinuity of the InGaP/InGaAsP heteroju nction was much smaller than the valence band discontinuity.