Three-color (λp1∼3.8 μm, λp2∼8.5 μm, and λp3∼23.2 μm) InAs/InGaAs quantum-dots-in-a-well detector

We report a three-color InAs/InGaAs quantum-dots-in-a-well detector with center wavelengths at $\text{∼3.8,}$ $\text{∼8.5,}$ and $\text{∼23.2\hspace{0.5em}μ}\mathrm{m}.$ We believe that the shorter wavelength responses (3.8 and $\text{8.5\hspace{0.5em}μ}\mathrm{m})$ are due to bound-to-continuum and bound-to-bound transitions between the states in the dot and states in the well, whereas the longer wavelength response $\text{(23.2\hspace{0.5em}μ}\mathrm{m})$ is due to intersubband transition between dot levels. A bias-dependent activation energy ∼100 meV was extracted from the Arrhenius plots of the dark currents, which is a factor of 3 larger than that observed in quantum-well infrared photodetectors operating at comparable wavelengths.