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

Abstract

Normal incidence InAs/In0.15Ga0.85As dots-in-a-well detectors operating at T=78 K with λp∼7.2 μm 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 (Vb=−1 V), peak detectivity=2.7×109 cm Hz1/2/W (Vb=−0.3 V), conversion efficiency of 57% and a gain ∼25.