GeSi based photodetectors and avalanche photodetectors on silicon photonics platform have been widely studied in the
past decade due to its low cost nature and compatibility with CMOS fabrication process. Conventionally, high-quality Ge
on Si is obtained by a direct epitaxy growth or by a wafer/die bonding technique, which complicates the possible on-chip
integration with CMOS electronics such as transimpedance amplifier, equalizer and limiting amplifier etc. Recently,
rapid-melt growth of Ge on insulator emerged as a new method to produce high-quality Ge stripes. In this paper, we
present our effort in making waveguide based photodetectors and avalanche photodetectors using Ge rapid-melt growth.
First, we demonstrate a high-performance, high-speed GeSi heterojunction photodiode by a self-aligned microbonding
technique utilizing surface tension. Such a method is subsequently extended to fabricate a novel butt-coupled, high-speed
metal-semiconductor-metal Ge photodetector. At the same time, we study the possibility of operating GeSi avalanche
photodetectors at a low bias voltage to be compatible with standard CMOS IC power supply. Based on the theoretical
and numerical results, a new type of GeSi avalanche photodetector in three-terminal configuration is proposed and
demonstrated, reaching the lowest possible operation bias voltage constrained by Zener tunneling breakdown.