Temperature-Dependent Characteristics of Germanium on Silicon Avalanche Photodiodes

The excellent performance of infrared image sensors and photonic integrated circuits (PICs) at low temperatures highlights the importance of elucidating the low-temperature physics of germanium-on-silicon avalanche photodiodes (Ge/Si APDs), which are key building blocks in such systems. In this work, the temperature-dependent physical characteristics of Ge/Si APD are systematically investigated through a combined experimental and numerical simulation approach. Furthermore, the evolution of key parameters governing Ge/Si APD performance under varying temperatures is explored. It is found that the surface recombination rate (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub>) between the Ge and silicon oxide (SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>) decreases with increasing temperature, while the electron lifetime (τ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub>) and the impact ionization electric field threshold (B) of Ge increase with increasing temperature. Therefore, at low temperatures, special emphasis should be placed on reducing dark current at the Ge/Si APD sidewalls and suppressing the electric field in Ge. The temperature dependence of these parameters provides a critical theoretical foundation for future structural optimization of Ge/Si APDs to achieve high performance at low temperatures.