INTERSUBBAND TRANSITIONS IN HIGH INDIUM CONTENT INGAAS ALGAAS QUANTUM-WELLS/

We report the first observation of intersubband transitions in InyGa1- yAs(Y=0.3,0.5)/AlGaAs quantum wells. These quantum wells were grown on a GaAs substrate with a linearly graded InGaAs buffer to achieve stra in relaxation before growth of the quantum wells. Measured intersubban d transition energies of 316 and 350 meV are among the largest ever re ported. Asymmetric step In0.5Gao.5As/AlGaAs quantum wells designed for second harmonic generation measurements also demonstrate strong inter subband absorption at 224 meV corresponding to the 1-2 transition. Wit h the large conduction band offsets (larger than 800 meV) available in this material system, extension to larger intersubband transitions en ergies for quantum well photodetector and nonlinear optics application s should be possible.