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A Novel Photosensitive Tunneling Transistor for Near-Infrared Sensing Applications: Design, Modeling, and Simulation

ABSTRACT:In this paper, a novel device structure, operating on the principle of band-to-band tunneling, has been designed for near-infrared (11.5 m) multispectral optical sensing applications. A drain current model based on line tunneling approach has been developed to illustrate the device operation. The results of the model are compared with the simulated data for devices with similar dimension and structure, indicating good accuracy of the developed model. Spectral response of the device is studied by estimating the relative values of its transfer as well as output characteristics, and also by measuring the variation of threshold voltage, VT and ON-state current, ION. VT and ION are found to be sensitive to wavelength variations at moderate gatedoping levels. VT is found to increase by 40 mV and ION decreases by 35% for a change of illumination wavelength from 1 to 1.5 m at a gate doping of 1 1018 cm3. Peak spectral sensitivity at an illumination intensity of 0.75 W/cm2 is found to be 318.38, 2.02 103, and 672.2 corresponding to the change in wavelength from (11.2 m), (1.21.45 m), and (1.451.5 m), respectively.

EXISTING SYSTEM:

NEAR-INFRARED multispectral biosensing and imaging finds a multitude of applications in the life sciences, compact on-chip spectroscopes for lab-on-chip systems, and noninvasive monitoring of blood oxygenation level. The requirement for low-cost biosensing devices, which could be integrated with CMOS technology, has burgeoned in the recent years. Such biosensing and imaging requires the detector to provide spectral differentiation among a discrete set of well separated wavelengths (e.g., >50 nm) [1][4]. Optically gated MOSFETs provide advantages of low-voltage operation, suitability for on-chip applications, and potential of superior noise performance due to the separated absorbing and conducting regions in comparison with avalanche photodiodes, which require high fields (20 V/m) to achieve desired ionization rates [5], [6]. For sensing a set of well separated wavelengths (e.g., >50 nm), the FET sensors are required to exhibit a wavelength-dependent conductance modulation due to secondary photoconductive effect. The optimal sensing domain for any FET-based sensor is the subthreshold regime [7].

PROPOSED SYSTEM:

In this paper, a novel photosensitive transistor, based on BTBT mechanism along the gate electric field, has been designed and a relevant transport model is developed to explain its operating principle. The similar device structure has also been simulated using Synopsys Sentaurus Device [16], a commercial device simulation package, for comparing its results with those obtained from the model for verifying its accuracy. The proposed device allows interesting features in terms of low operating voltage (