Heterojunction photodiodes fabricated from Ge/Si (1 0 0) layers grown by low-energy plasma-enhanced CVD

Abstract

We have fabricated a series of p-i-n Ge/Si heterojunction photodetectors with different thicknesses of the nominally intrinsic Ge layer. Epitaxial Ge was deposited on Si(1 0 0) using low-energy plasma-enhanced CVD (LEPECVD) followed by cyclic annealing. The residual tensile strain induced by the annealing procedure lowers the direct energy gap EΓ by ΔEΓ = 20 meV, increasing the responsivity at the Ge absorption edge. Responsivities of 350 mA W−1 at 1.30 µm and 470 mA W−1 at 1.55 µm were obtained for a 3 µm thick photodiode under 3V reverse bias.