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

Abstract

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).

Analytical model for threshold‐base current of a transistor laser with multiple quantum wells in the base

“…The optical gain in strained QW is calculated considering two-dimensional (2D) density-of-states, Fermi golden rule and broadening of states. The values of threshold-base current, light power output and the charge carrier distribution profile obtained in this work agree satisfactorily with the experimental results reported by Feng and his co-workers [5,7,8,12,13].…”

“…4, the ordinate, that is, the QW positions in base, refers to the position of the QW in single QW-TL and the positions for the middle QW for both the symmetric and asymmetric TLs. The plot for SQW has already been obtained in [11] and the value of 21.5 mA for I Bth for QW position of 59 nm has been in complete agreement with the experimental value [5,7]. With the middle QW placed at 59 nm, the value is 8.96 and 7.06 mA, respectively, for the AMQW and symmetric MQW (SMQW)-TL.…”

“…The group also presented some analytical models [5,6] to predict or explain the current-voltage and light-current characteristics and the modulation bandwidth [6,7]. A circuit model has also been developed by the group [8].…”

Gain-bandwidth trade-off in a transistor laser: quantum well dislocation effect

“…1 that bandwidth increment may result in a decrease in current gain (β). For a QW transistor laser with stimulated base recombination, the base current and current gain can be expressed as (Feng et al 2006b):…”

Spectral characteristics of a 1.3-µm npn-AlGaInAs/InP transistor laser under various operating conditions

“…In addition, the TL has the potential to break the modulation speed limitations inherent in conventional LDs because shorter carrier recovery times can be achieved [5,6,7,8,9,10]. Until now, several studies on the 0.98-µm TLs have been have been conducted [11,12,13]. In our previous reports, we successfully achieved the first room-temperature continuous-wave (RT-CW) operation at longer wavelengths as well as the transistor characterization of a pnp [14] and an npn TL emitting at the 1.3-µm wavelength using an AlGaInAs/InP material system [15].…”