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

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 E?by ?E?= 20 meV, increasing the responsivity at the Ge absorption edge. Responsivities of 350 mA W?1at 1.30 µm and 470 mA W?1at 1.55 µm were obtained for a 3 µm thick photodiode under 3V reverse bias. [ABSTRACT FROM AUTHOR]