Multiplied absorption in subwavelength self-grating-coupled multi-layer quantum wells with reduced dark current

Abstract

Light detection through intersubband transition faces combined demands of retaining normal incidence coupling, enhancing absorption, and suppressing dark current which is usually fulfilled by separate parts in devices. In this paper, 50-period GaAs/AlGaAs quantum well (QW) layers are designed and fabricated into arrays of subwavelength columns, which induces resonant mode to confine the infrared light inside the columns with strengthened electric field component in the z-direction. The self-grating-coupled QWs exhibit broadened absorption in the long wavelength range with peak absorption increased by 4.5 times at 8.7 μm relative to that of the 45⁰ polished edge-coupled counterpart. Meanwhile, the dark current is reduced by 51% due to the reduction of the electrical area. With the joint benefits of guiding and compressing incident light in squeezed volumes, it’s demonstrated that the dark current limited specific detectivity (Ddark∗) of quantum well infrared photodetectors (QWIPs) could be raised by 6.4 times when merged into photonic structures.