Technique for integration of vertical cavity lasers and resonant photodetectors

Abstract

We demonstrate a design that allows fabrication of substrate input/output resonant-cavity photodetectors and vertical cavity lasers (VCLs) on the same substrate without regrowth. By selectively oxidizing a few layers in the bottom mirror the as-grown 80% reflectivity mirror, used as the input mirror for the detector, is converted to a 99.3% reflectivity mirror allowing fabrication of VCLs from the same epitaxial material. Since these two reflectivities are uncorrelated, the detectors and VCLs can be individually designed. Despite the change in refractive index from ∼3 to ∼1.6 in the oxidized layers, the structure can be designed to have nearly the same resonance wavelength for both the detectors and VCLs. Using this design strategy, we have successfully fabricated high-performance resonant photodetectors and VCLs from the same epitaxial material. The photodetectors have an absorption of 56% and an optical bandwidth of 5.9 nm, in good agreement with theory. Small diameter, single-mode VCLs have threshold currents as low as 180 μA with 33% slope efficiencies while multimode devices have slope efficiencies exceeding 60% with less than 500 μA threshold currents.