ON THE EFFECTS OF CARRIER DIFFUSION AND QUANTUM CAPTURE IN HIGH-SPEED MODULATION OF QUANTUM-WELL LASERS

It is shown that, the combined effects of carrier diffusion in the separate confinement heterostructure region and quantum capture into the quantum well must be considered together when evaluating the limits on the modulation bandwidth of quantum well lasers, despite the fact that quantum capture is considerably faster than carrier diffusion. The importance of quantum capture may be observed by noting that the modulation bandwidth is adversely affected even for quantum capture times as short as 0.2 ps, or if the ratio of the quantum capture time to quantum escape time is large (> 0.01). Therefore, the bandwidth limitation may be caused by electron transport rather than hole transport since quantum capture of holes is faster than that of electrons.