Intersubband Dynamics in Semiconductor Quantum Wells

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This theoretical grant focuses on the nonlinear response associated with intersubband transitions in semiconductor quantum wells. Typical subband splittings in quantum wells grown from the GaAs/AlAs and InAs/GaAs systems are in the far- to the mid-infrared region of the spectrum - from 1 to 100meV. In wide-bandgap III-V materials, such as InGaN/GaN and GaN/AlGaN quantum wells, intersubband splittings from the far- to the near-infrared are possible.The follwing project swill be addressed:Carrier-wave Rabi flopping: These are population oscillations between two subbands driven coherently up and down by a strong THz pulse in wide GaAs/AlGaAs quantum wells.Nonlinear far-infrared response: A wide n-type GaAs/AlGaAs quantum well driven by a strong field near an intersubband transition may exhibit an essentially nonlinear response owing to intersubband plasmons, which screen out the driving field.Intersubband carrier dynamics in GaN/AlGaN and InGaN/GaN quantum wells: Wide-bandgap nitride quantum wells may possess built-in electric fields as large as ~1MV/cm - in excess of dielectric breakdown fields in lower-bandgap semiconductors. The dynamic screening of this polarization field as an intersubband tranition is driven by a THz source will lead to a strong nonlinear response.Each topic will be studied in close cooperation with experimental groups at Michigan, UCSB and Georgia Tech. %%%This theoretical grant focuses on the nonlinear response associated with intersubband transitions in semiconductor quantum wells. These transitions can lead to many novel phenomena of both fundamental and applied interest. The research will be done in close coordination with leading experimental groups.***