Direct MBE growth of metamorphic nBn infrared photodetectors on 150 mm Ge-Si substrates for heterogeneous integration

Abstract

GaSb-based infrared (IR) photodetector structures were grown on large diameter, 150 mm, Si substrates using a multistep metamorphic buffer architecture process. A standard bulk InAsSb/AlAsSb barrier detector design with a cutoff wavelength of ∼4 μm was used as a test vehicle for this growth process. First, a Ge layer was deposited by chemical vapor deposition, creating a Ge-Si substrate for the subsequent molecular beam epitaxy growth of the remaining III–V buffer and device layers. X-ray diffraction and photoluminescence measurements demonstrated high crystal quality and excellent cross-wafer uniformity of the device epiwafer characteristics. Microscopy evaluation revealed a moundlike surface morphology with a low root-mean-square roughness value below 2 nm, suitable for focal plane array (FPA) fabrication. Large-area mesa diode test devices measured dark currents of 5 × 10−5 A/cm2 and a quantum efficiency of 60% for the Sb-detector grown on Ge–Si. The same structure was fully fabricated into a standard FPA and produced good imagery resolution with high operability. These excellent results for this first FPA manufactured from an Sb-photodetector grown on Si using this Ge-Si architecture demonstrate a promising path in the progression of Sb-IR technology as it transitions from development to next-generation, large-format IR manufacturing with an eye toward potential heterogeneous integration with silicon.