Carrier lifetime and modulation bandwidth of a quantum well $AlGaAs∕InGaP∕GaAs∕InGaAs$ transistor laser

A quantum well $(160Å)$ transistor laser with a $400μm$ cavity length that achieves the large $3dB$ modulation bandwidth of $13.5GHz$ is described. The fast base recombination (transport determined, $τBL<10ps$⁠) permits improvement of the carrier-photon damping ratio $(>1∕2)$⁠, resulting in a resonant peak magnitude of unity and consequently a resonance frequency of $∼0GHz$ (no peak) in the small-signal response. Quantum well band filling and bandwidth saturation are observed on the ground state $(λ=1000nm)$⁠, and increase with operation on the first excited state $(λ=980nm)$⁠.