Photovoltaic In0.5Ga0.5As/GaAs quantum dot infrared photodetector with a single-sided Al0.3Ga0.7As layer

We investigated a photovoltaic three-stacked In0.5Ga0.5As/GaAs quantum dot infrared detector (QDIP) with an Al0.3Ga0.7As single-sided blocking layer. We observed broad photocurrent spectra in the photon energy range of 120-400 meV (λ ∼ 3-10 μm) at zero-bias voltage, due to the photovoltaic effect at low temperatures. The peak responsivity was about 10.5 mA/W at a photon energy of 200 meV (λ ∼ 6.2 μm) at T = 40 K. The large photovoltaic effect in our detector was a result of the enhanced asymmetric band structure, caused not only by the segregation of highly doped Si atoms, but also by the single-sided Al0.3Ga0.7As layer beneath the top contact layer.