InGaAs/Si Avalanche Photodiode With High Gain and Low Dark Current Achieved by Two-Step Wafer Bonding

The integration of InGaAs with Si presents considerable challenges due to lattice mismatch and the difference in thermal expansion coefficient, interfacial impurities, and bubbles. To address these issues, a novel approach, in which the microcrystalline Ge including polycrystalline Ge and monocrystalline Ge as the bonding interlayer, is proposed to successfully achieve high-quality InGaAs/Si-bonded heterojunction. A high-pure Si multiplication layer is prepared via Si film stripping technology based on Si/Si wafer bonding. The plasma surface treatment and water ultrasonic processing are used to enhance the quality of the Si/Si-bonded interface for the well carrier transport. The InGaAs/Si avalanche photodiode (APD) fabricated by the two-step wafer bonding method is achieved, demonstrating a high gain of 235, a responsivity of 2.31 A/W, and an exceptionally low temperature coefficient of the breakdown voltage of 0.088%. More importantly, at the near-room temperature of 195 K, the device exhibits a dark current density as low as 0.052 mA/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, highlighting its promising potential for advanced optoelectronic applications.