Growth and Characterization of Long-Wavelength Infrared Type-II Superlattice Photodiodes on a 3-in GaSb Wafer

We report the molecular beam epitaxial growth and characterization of high-performance Type-II superlattice photodiodes on a 3-in GaSb substrate for long-wavelength infrared detection. A 7.3-μm-thick device structure shows excellent structural homogeneity as demonstrated by atomic force microscopy and X-ray diffraction characterization. Optical and electrical measurements of the photodiodes reveal not only the uniformity of the Type-II superlattice material but also of the fabrication process. Across the wafer, at 77 K, photodiodes with a 50% cut-off wavelength of 11 μm exhibit more than 45% quantum efficiency and a dark current density of 1.0 × 10 ^-4 A/cm ² at 50 mV, giving a specific detectivity of 6 × 10 ¹¹ cm Hz ^1/2 /W.