PREVENTION OF BASE DOPANT OUT-DIFFUSION USING A HETEROSTRUCTURE-EMITTER IN GAINP GAAS HETEROJUNCTION BIPOLAR-TRANSISTORS/

Zinc-doped GaInP/GaAs heterojunction bipolar transistors (HBTS) grown by MOCVD were fabricated. Characteristics of HBTS with an undoped spac er layer and an n-type GaAs set-back layer (heterostructure-emitter) b etween base and emitter were investigated. The results show that the b ase dopant out-diffusion was effectively prevented in heterostructure- emitter bipolar transistors (HEBTS). In addition, a current gain of 10 0 at the collector current density of 1 x 10(-2) A cm(-2) and an offse t voltage of 57 mV were obtained for Zn-doped HEBTS. In comparison wit h carbon-doped HBTS, HEBTS offer a higher current gain at a low curren t level, a smaller offset voltage and better uniformity in characteris tics across the wafer.