Large Energy Intersubband Transitions in High Indium Content InGaAs / AlGaAs Quantum Wells

Abstract

Large energy intersubband transitions are necessary for extending intersubband applications to the near-infrared (≤ 2μm wavelength) where compact diode laser based sources are available. By growing high indium content InGaAs / AlGaAs quantum wells (QWs) on GaAs substrates with linearly graded InGaAs buffers, we have demonstrated peak intersubband absorption energies as high as 580meV (2.1μm wavelength). We have also demonstrated intersubband absorption at 580meV in asymmetric coupled InGaAs / AlAs QWs. These are the largest bound-to-bound intersubband transition energies to date. Experimental studies of buffer and QW growth parameters for optimized intersubband absorption have been performed. The well width dependence of intersubband transition energies in both In0.5Ga0.5As / Al0.45Ga0.55As QWs and In0.5Ga0.5As / AlAs QWs have been measured and theoretically modelled.