Ultrafast Carrier Dynamics And Optical Nonlinearities Of Low-Temperature-Grown Multiple Quantum Wells

The ability to engineer the free carrier lifetime of epitaxially grown semiconductors without significantly affecting the desirable nonlinear optical properties would allow the development of an entire new class of high-speed photonic devices. The primary method of achieving this is the controlled introduction of mid-gap defects via a variety of techniques including low temperature growth. We report on a systematic investigation of low-temperature-grown materials including bulk GaAs and Be-doped In0.53Ga0.47As/In0.52Al0.48As multiple quantum wells. Using both wavelength-dependent time-resolved nonlinear bandedge absorption spectroscopy and far infrared Terahertz spectroscopy, we unambiguously discriminate between recombination and trapping events and determine the carrier lifetime and mobility in a contactless fashion. We correlate the far infrared response and the bandedge response and thereby explain the apparent discrepancies with previous measurements and clarify the physical origin of the optical nonlinearity as well as the defect densities, carrier lifetimes and mobility.