Ultrafast 1.55-μm photoresponses in low-temperature-grown InGaAs/InAlAs quantum wells

Abstract
Doping with Be was found to be very effective for shortening of carrier lifetime in InGaAs/InAlAs multiple quantum wells (MQWs) grown at low temperature by molecular beam epitaxy. The MQW materials have carrier lifetimes controllable from a few tens of picoseconds to 1 ps in the 1.55‐μm wavelength region, coupled with a large optical nonlinearity due to an excitonic feature, implying applicability to ultrafast optical devices in the fiber‐optic communication. The carrier lifetime was measured by a time‐resolved pump‐probe method using an optical source based on a 1.535‐μm semiconductor laser. We also investigated the resistivity, carrier density, and Hall mobility in the MQWs.