Normal-incidence mid-infrared photodetection via intraband transitions in InGaAs/InP multiple quantum well nanowire arrays

Recently, InGaAs/InP multiple quantum well nanowires grown by selective area epitaxy have been demonstrated with uniform morphology and high optical quality. The InGaAs quantum wells wrapping around the nanowire core are formed with both axial and radial components. As such the radial quantum well configuration presents a unique advantage for the realization of intraband absorption of normal-incidence light in the nanowires, which cannot be achieved in conventional planar quantum well structures due to polarization selection rules. We report here mid-infrared intraband transitions within the atmospheric window (3–5 μm) in InP nanowire arrays embedded with five InGaAs quantum wells under normal-incidence light. The light absorption coefficient of the quantum wells is modeled, and the absorption peak indicates a bound-to-continuum transition. The intraband photocurrent shows a linear dependence on the incident power, while the interband photoresponse is sublinear due to the surface states of the nanowires. These nanowires with radial quantum wells open up great opportunities for developing next-generation mid- to long-wavelength infrared photodetectors and focal plane arrays.