Comparison of GaInP/GaAs heterostructure-emitter bipolar transistors and heterojunction bipolar transistors

Carbon-doped GaInP/GaAs heterojunction bipolar transistors (HBT´s) and heterostructure-emitter bipolar transistors (HEBT´s) grown by MOCVD were fabricated. Experimental comparison of HBT´s and HEBT´s has been made based on the dc and the RF performance. HBT´s have higher current gains than those of HEBT´s in the high current regime, while HEBT´s offer a smaller offset voltage and better uniformity in dc characteristics across the wafer. The current gain and cutoff frequency of the DEBT with a 150 Å emitter set-back layer are comparable to those of HBT´s. DC (differential) current gains of 600 (900) and 560 (900) were obtained at a collector current density of 2.5×10⁴ A/cm² for the HBT and HEBT, respectively. The cutoff frequencies are 37 and 31 GHz for the HBT and HEBT, respectively. It is shown that there is negligible contribution of the diffusion capacitance to the emitter capacitance in HEBT´s with a thin emitter set-back layer but not with a thick emitter set-back layer. The behavior of HEBT´s both in dc and RF characteristics is similar to that of HBT´s