Abstract

Monolithic silicon sub-bandgap avalanche photodetectors are fabricated using the introduction of lattice defects to silicon waveguides through silicon ion implantation and annealing. The devices are characterized using light at a wavelength of 1550 nm. Through control of implantation dose we create a low-absorption device with 0.4 dB (5.4 dB/cm) excess optical absorption, and a high-absorption device with 3.2 dB (42 dB/cm) excess optical absorption. The low-frequency unity-gain bias point, M = 1, is approximately 12 V for both devices. Increasing reverse bias results in electrical gain such that M = 35 at 32 V for the high-absorption device, with associated responsivity of 13 A/W for coupled optical power ranging from −20 dBm to −5 dBm. The electrical bandwidth of this device peaks at 10 GHz for M = 14 and decreases to 6 GHz for M = 35. The RC limited bandwidth of an unimplanted, control device is measured to be 26 GHz. The gain-bandwidth product of the high-absorption device is 230 GHz. Measurement of the excess noise factor provides an effective k-value of 0.1, consistent with the gain-bandwidth product. Primary carriers in the avalanche process are predominatly electrons, with a carrier ionization threshold of ∼ 0.6eV, indicating for the first time in this device type that both the light detection and avalanche process are mediated by the deep-levels.