Near-infrared intersubband transitions in InGaAs/AlAs quantum wells on GaAs substrate

We report intersubband transitions in InGaAs/AlAs quantum wells on GaAs substrate. The intersubband-transition wavelength and absorption coefficient are investigated as functions of sample structure and growth conditions. It is shown that a decrease in well width leads to a shorter transition wavelength but a reduction in the absorption coefficient. The reduction in the absorption coefficient can be recovered by increasing the In composition of the well and by suppressing the segregation of In during growth. With these optimizations, a very short intersubband-transition wavelength of 1.9 mu m is achieved.