Investigation of Random Telegraph Noise in the Dark Current of Germanium Waveguide Photodetector

Dark current variations in the germanium waveguide photodetector were investigated. Contributing to the time dependent dark current variations, random telegraph noise (RTN) was observed and studied for the first time. The RTN at different reverse biases and temperatures were measured. By analyzing the capture and emission time constants, the single trap that was responsible for RTN was estimated to be around 18 nm from the interface between the N ⁺⁺ and the intrinsic region. The trap energy levels at different reverse biases were also extracted and the trapping and detrapping dynamics were explained. Through this procedure, the single trap that may lead to device failure can be detected and characterized without destroying the well-fabricated devices.