Uniformly doped InAs/GaAs quantum-dot infrared photodetectors with AlGaAs current blocking layer

We report a study of uniformly doped InAs/GaAs quantum-dot photodetectors with Al_0.3Ga_0.7As current-blocking layers. The basic device structure contains fifty periods of InAs/GaAs dots. The GaAs barrier layer, as well as the InAs quantum dots, are uniformly doped with Si (2×10¹⁶ cm^-3) to supply electrons to the quantum-dots. For a -0.3 V bias, the dark current could be reduced by six orders of magnitude when the temperature is lowered from 300 to 78 K. The peak of the photoresponse spectrum of our devices is around 5.5 μm. The large peak energy of about 236 meV and the Δλ/λ∼55% at the peak response suggest that the transitions are from bound levels to the continuum. The peak responsivity of the detectors is about 0.20 Amp/W at 78 K.