High-Performance Ge PIN Photodiodes on a 200 mm Insulator with a Resonant Cavity Structure and Monolayer Graphene Absorber for SWIR Detection

Abstract

High-responsivity and low dark current resonant-cavity-enhanced (RCE) Ge PIN photodiodes with a monolayer graphene absorber were demonstrated on a 200 mm insulator. Ge was grown on the donor Si wafer, whereas the acceptor wafer contained a two-period poly-Si/SiO2 as a distributed Bragg reflector (DBR) mirror. Then, a direct wafer-bonding technique was adopted to transfer the Ge layers on the poly-Si/SiO2 DBR mirror, thereby forming the RCE Ge PIN photodetectors on the insulator with mesa diameters ranging from 10 to 100 μm. At −1 V reverse bias voltage, average responsivities of 0.67 and 0.85 A/W at 1550 and 1310 nm were achieved due to the combined function of poly-Si/SiO2 DBR mirror, high-quality Ge active layer, and 2D graphene. The monolayer graphene was transferred from a Cu foil on the chips, which increased the responsivity of the Ge PIN photodetectors at 1310 and 1550 nm by 11.6 and 7.6%, respectively. The dark currents of the detectors at room temperature were in the nanoampere range, for example, the 10 μm detector exhibited a dark current of 5.75 nA. The novelty of our results is based on the integration of a novel DBR mirror below the Ge PIN photodetectors with a graphene absorber on the top. This indicates a significant improvement in the performance of the current Ge PIN photodetectors and a promising technique route to optimize the low-cost and CMOS-compatible short-wave infrared imaging chips in the near future.