Femtosecond response time in beryllium-doped low-temperature-grown GaAs/AlAs multiple quantum wells

We have investigated optical nonlinearity in beryllium-doped low-temperatur e (LT) molecular-beam-epitaxy-grown GaAs/AlAs multiple quantum wells (MQWs) . The response time of the nonlinearity is reduced by Be doping in the MQW. While the undoped LT MQW shows a 0.7-0.9 ps response, the response time of the Be-doped LT MQW is as short as 0.25 ps. The saturation density of the Be-doped MQW is almost the same as that of the undoped MQW, and is smaller than that of bulk GaAs. These results demonstrate that the Be-doped LT MQW exhibits a faster response than the undoped LT MQW, and a faster response a s well as larger nonlinearity than LT bulk GaAs. (C) 2001 American Institut e of Physics.