Carrier transport effects in undoped In0.35Ga0.65 As/GaAs MQW lasers determined from high-frequency impedance measurements

The authors have recently reported the use of high-frequency impedance measurements to obtain information about the carrier capture/re-emission processes in ultra-high-speed (30 GHz modulation bandwidth) p-doped In_0.35Ga_0.65As/GaAs MQW lasers. By using this approach the authors demonstrated: i) that the interplay between carrier capture and re-emission is not strongly affecting the high-speed modulation dynamics of these devices; and ii) that a bias dependent RC like roll-off with an associated time constant τ₀ , is still limiting the modulation bandwidth. In the paper the authors apply the impedance method to lasers with the same epilayer structure as those reported previously, but with nominally undoped active layers. In addition to the time constant τ₀ they were able to extract the carrier re-emission time out of the QWs, τ _esc, and the effective carrier lifetime in the QWs, τ_eff