GSMBE growth of InGaAsP step-graded composite collector structure applied to DHBT

A new InP/InGaAs/InP DHBT structure with step-graded composite collector was designed in this work. Two InGaAsP layers with different band gaps were inserted between collector and base of DHBT to eliminate the electron blocking effect. The InP/InGaAs/InP DHBT structure was grown by gas source molecular beam epitaxy (GSMBE). Good crystalline quality of InGaAsP materials were obtained through optimizing the growth condition. The DHBT device with emitter area of 100×100μm2 and 0.8×15μm2 was fabricated, respectively. The offset voltage of 0.2V, BVCEO>4V, fT of 170GHz and fmax of 253GHz were achieved. These results indicate that the InP/InGaAs/InP DHBT is suitable for low power-dissipation and high power applications.