High-Gain Photodetector to Realize an Integrated Portable Spectrum Analyzer

The application of color sensors plays a crucial role in a wide range of fields, including quality control, environmental monitoring, industrial, and biological research, by enabling precise color detection and analysis. In this paper, we present a high-gain color sensor in which the filter and photodetector are implemented in an integrated structure. The proposed photodetector consists of a multilayer color sensor placed on the base of an NPN bipolar junction transistor. The incoming visible light can be detected separately by a multilayer color sensor including three isolated parts for red, green, and blue sections of the spectrum. The green part of the visible spectrum is investigated herein. Two other parts can be realized by adjusting the layers’ thicknesses of the sensor. The transmitted photons through the filter are converted into an electrical current and also amplified by an NPN bipolar junction transistor (BJT). The BJT causes the output current from the photodetector to increase due to the intrinsic current amplification of the transistor (β). The peak wavelength of the transmission spectrum is shifted from 540 to 500 nm by applying 15V for a visible light intensity of 100mW/cm2. Furthermore, the output characteristic of the transistor is reported under the base-emitter voltage of 0.25V.