Scaling of light emitting transistor for multigigahertz optical bandwidth

We report for an $n-InGaP/p-AlGaAs/i-InGaAs-QW/n-GaAs$ heterojunction bipolar light emitting transistor (HBLET) the record spontaneous optical-signal bandwidth, at −3 dB, of 1.8–4.3 GHz (corresponding to an effective carrier recombination lifetime of 37 ps). Besides the improved circuit matching of three-terminal device operation, the extension in performance is achieved by the lateral reduction in the emitter aperture size $DA$ from 13 to $5μm$ to provide higher injection current densities and better confinement of the radiative recombination in the base region. By reducing the carrier loss to lateral extrinsic recombination, we obtain with HBLETs higher current gains $β(=ΔIC/ΔIB>30)$ and simultaneously $>4GHz$ optical bandwidths.