Strain—Engineered Asymmetrical Si/Si1–xGex IR-Photo-Detector: Theoretical Reliability and Experimental Feasibility Studies

This paper reports the prospect of strained Si/Sin _1–x Ge _x nano-scale p ⁺⁺ -i-n ⁺⁺ photo-detector in the infrared (IR) wavelength region (1000 nm–2200 nm). The proposed device is capable of offering high photo-responsivity and quantum efficiency at 1600 nm wavelength in comparison to the unstrained conventional Si based pin photo-detector device. The authors have developed a Quantum Modified Drift Diffusion Model to analyze the nano-scale properties of strained Si photo-detector device. The analysis reveals that the strained Si based pin photo-detector offers high photo responsivity 0.67 A/W at 1600 nm wavelength and quantum efficiency 0.60 at the same wavelength compared to the conventional unstrained Si based photo-detector. The enhancements of the photo electric characteristics of the Si photo device are obtained by incorporating selective amount of Ge into the Si active region. The electrical properties in the strained Si semiconductor at room temperature (300 K), have made this material more attractive for being used as a photo-detector. Due to the incorporation of this Ge layer, in-plane bi-axial strain is produced in the active region. This phenomenon enhances the out-of-plane mobility of charge carriers. In this current research, in-plane strain is used to boost up the out-plane mobility depending on the geometrical structure of the active region. The validity of the proposed model is established by comparing the simulated data with the corresponding experimental results. The authors also report the reliability study of the proposed device in details. Further, the authors have developed a 4 $\times$ 4 array type photo-detector based on the strained Si structure and the results are compared with the corresponding single array type photo-detector. In case of the 4 $\times$ 4 array type photo detector, the photo electric characteristics, i.e., photo responsivity and quantum efficiency increase to 0.74 A/W and 0.69 respectively at 1600 nm wavelength. In IR wavelength region, the designed photo-sensor depicts a significant improvement of performance compared to the available photo-detector in published research work. The proposed photo-detector can play an important role in Bio-medical, Defence and Agro industries. According to the authors’ knowledge, this is the first report on strain engineered nano scale asymmetrical Si/Si _1–x Ge _x based photo-detector array.