A CMOS compatible Ge-on-Si APD operating in proportional and Geiger modes at infrared wavelengths

A CMOS compatible Ge avalanche photodiode is fabricated on Si by using a selective chemical-vapor deposition (CVD) epitaxial growth technique. At a temperature of 700°C, single crystal islands of As-doped Ge are grown in windows to the Si with sizes up to hundreds of µm2, to a layer thickness of approximately 1 µm, This is followed by a pure Ga and then a pure B (PureGaB) deposition for the creation of an ultrashallow p
⁺
-region that can be metallized by Al. The resulting p
⁺
n diodes have exceptionally good I–V characteristics with ideality factors of ∼ 1.1 and reliably low saturation currents. The measurements show high sensitivity of the photodiodes to IR wavelengths above 1µm in avalanche and Geiger modes.