Design and characterization of asymetrical super-lattice Si/4H-SiC pin photo diode array: a potential opto-sensor for future applications in bio-medical domain

Photo-sensors are integral part of different bio-medical diagnostic equipment. Each type of bio-molecules possess unique spectral fingerprint in visible wavelength region of electro-magnetic spectrum. Now-a-days, the enhancement of quantum-efficiency and photo-responsivity of such bio-medical opto-sensors, for accurate identification of virus/anti-bodies in blood by optical means, is a big challenge to medical-device Engineers. The authors have addressed this issue in this research paper by proposing a novel structure of asymmetrical Si/4H-SiC super-lattice pin diode array for the development of high-sensitive visible light (300–800 nm) sensor on native substrate. The simulation experiment is carried out by developing a generalized large-signal quantum modified drift–diffusion simulator incorporating three different modes of carrier generation-recombination under light and dark conditions: avalanching, tunneling and photo-irradiation. The validity of the model has been established by comparing the simulation results with those of experimental observations. A good agreement between theory and experiment, under similar biasing conditions, establishes the validity of the developed model. The characteristics analysis depicts that the quantum efficiency of the designed single photo-sensor is ~ 65% within 400–700 nm wavelength region, whereas, the same enhances to nearly ~ 90% with a 3 × 3 photo-sensor array based on asymmetrical super-lattice single pin devices. In visible wavelength region, the simulated photo-sensors (both single and array) have demonstrated significant photo responsivity. The photo-responsivity values, at 500 nm wavelength of incident radiation, are observed to be 0.65 A/W for a single photo-diode and 0.85 A/W for a 3 × 3 combination of photo-diode array. This clearly establishes the potentiality of the asymmetrical super-lattice pin-array as a visible photo-sensor for future application in developing medical instruments. A comparative analysis of Si and Si/4H-SiC asymmetrical super-lattice photo-sensors establishes the superiority of the later as a high-sensitive visible light-sensor in terms of better photo-responsivity and quantum efficiency. To the best of authors’ knowledge, this is the first report on Si/4H-SiC super-lattice pin photo-sensor array in the visible range of optical irradiation. The experimental feasibility of the device and a proposed circuit for future bio-medical implementation are also incorporated in the present research-paper for further development.