InGaAsP/InP heterojunction bipolar transistor grown by MOVPE

Abstract An InGaAsP( λ g = 1.2 μ m)/InP DHBT for use wavelength (1.3—1.55 μm) OEICs has been successfully fabricated, on a semi-insulating Fe-doped InP substrate, by a low pressure MOVPE method. Current-voltage characteristics of the emitter-base and base-collector junctions exhibit ideality factors of 1.81 and 1.34, respectively, and almost the same built-in voltages of 0.9 V, indicating that the p-n junctions are formed at the heterointerfaces of p-InGaAsP and n-InP, which is consistent with a SIMS analysis of the impurity depth profile. The common emitter characteristics of a typical DHBT show no offset voltage, small Farly effect, and a higher breakdown voltage of more than 10 V. The current gain ( h FE ) is about 160 at a collector current ( I c ) of 10 mA. The h FE has a small dependence on I c in the range from 1 μA to 10 mA ( h FE ∼ I 0.25 c ). The dependence of the cutoff frequency ( f T ) on the I c shows that the best f T is 3.6 GHz at I c = 20 mA.