High-responsivity, normal-incidence long-wave infrared (λ∼7.2 μm) InAs/In0.15Ga0.85As dots-in-a-well detector

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Abstract
Normal incidence InAs/In 0.15 Ga 0.85 As dots-in-a-well detectors operating at T=78 K with λ p ∼7.2 μ m and a spectral width (Δλ/λ) of 35% are reported. The peak at 7.2 μm is attributed to the bound-to-bound transitions between the ground state of the dot and the states within the InGaAs well. A broad shoulder around 5 μm, which is attributed to the bound-to-continuum transition, is also observed. Calibrated blackbody measurements at a device temperature of 78 K yield a peak responsivity of 3.58 A/W (V b =−1 V ), peak detectivity =2.7×10 9 cm Hz 1/2 / W (V b =−0.3 V ), conversion efficiency of 57% and a gain ∼25.