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

Abstract

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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -region that can be metallized by Al. The resulting p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> 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.