Effect of Be doping on the absorption of InGaAs/AlGaAs strained quantum-well infrared photodetectors grown by molecular-beam epitaxy

We report on the effect of Be doping in the well layers on the absorption of the p-type strained InGaAs/AlGaAs quantum-well infrared photodetectors. It is found that the absorption spectrum originated from the bound-to-bound intersubband transition shifts towards the low-wavelength side as the doping density is increased, due to the band gap shrinkage and widened well width. The full width at half maximum of the absorption spectrum increases with doping density due mainly to the increased roughness at the well-barrier interfaces. The observed results are in good agreement with the estimated values after taking the compressive strain, band gap shrinkage of the well layers, and the increased well width into account. (C) 1999 American Institute of Physics. [S0003-6951(99)03611-6].