Gas Source MBE-Grown Metamorphic InGaAs Photodetectors using InAlAsBuffer and Cap Layers with Cut-off Wavelength up to 2.7

We report on InP-based metamorphic InGaAs photodiodes grown by gas
source molecular beam epitaxy (MBE), in which a relatively thin compositional graded wide band-gap In_xAl_1-xAs buffer layer is adopted. In the photodiodes, InAlAs is also taken as cap layers, so this structure is suitable for both front and back illuminations. At room temperature the photodiodes show 50% cut-off wavelength of 2.66μm, with measured peak detectivity of 4.91×10⁹cmHz^1/2/W at 2.57μm, and the typical dark current and R₀A are
7.68μA/0.94Ωcm² and 291nA/24.29Ωcm² at 290K and 150K respectively for the devices in diameter 300μm. Their performances are compared to the 2.5-μm cut-offphotodiodes with similar structures.