Efficient Er/O Doped Silicon Photodiodes At Communication Wavelengths By Deep Cooling

Wide band infrared photodetectors have found a wide range of applications in sensing, communication, and spectral analysis. However, the commonly used infrared photodetectors are based on Ge and III-V semiconductors which are not complementary metal-oxide-semiconductor (CMOS) compatible and therefore have limited applications. There is a huge demand for silicon-based infrared photodetectors due to its low-cost and compatibility with CMOS processes. Nevertheless, the spectral bandwidth of Si photodetectors is limited to wavelengths below 1.1 mu m. Several approaches are developed to extend Si photodetection bandwidth to communication wavelengths. Er/O doped Si is a promising approach which, however, suffers from low infrared responsivities at room temperature when the samples are treated with the standard rapid thermal annealing (RTA). In this work, a novel deep cooling process to treat Er/O doped silicon waveguide photodiodes is applied. In comparison with RTA process, the deep cooling process reduces the defect concentration in silicon by two orders of magnitude, resulting in a two-orders-of-magnitude reduction in leakage current density and an enhanced photoresponsivity to 100 mA W-1 at 1510 nm. The 3dB bandwidth of the silicon waveguide photodiode reaches 30 kHz. The device performance can be further improved by optimizing the deep cooling condition and Er/O doping concentration.