Development of n-TiN/p-CdTe/n-CdTe Phototransistors for Use in a Networked Digital Light Sensor

In this work, the mode of production by reactive magnetron sputtering of n-TiN/p-CdTe/n-CdTe heterostructures, which have the properties of a phototransistor with an unconnected (floating) base, is investigated. It is shown that in the structure of n-TiN/p-CdTe/n-CdTe at reverse voltage at the collector junction of p-CdTe/n-CdTe under conditions of irradiation close to АМ1 from the side of the n-TiN emitter, the phenomenon of amplification of the collector photocurrent by the direct current of the directly switched on is observed of the n-TiN/p-CdTe heterojunction. A forward voltage is applied to the n-TiN/p-CdTe heterojunction due to the positive charge of the p-CdTe base during illumination. Photoelectric phenomena during illumination of the n-TiN/p-CdTe/n-CdTe heterostructure were analyzed. The purpose of this work is to evaluate the practical use of the newly created n-TiN/p-CdTe/n-CdTe heterostructure in the phototransistor mode of operation to create an illumination sensor with a digital interface for use in network control and management systems. The possibility of using the manufactured transistor as a digital illuminance sensor for large values of light flux is substantiated. The phototransistor was used as the primary converter for the microcontroller, which includes a functional block of the operational amplifier. The phototransistor and the operational amplifier together implement the photocurrent-voltage converter system. This solution allows you to use the internal operational amplifier of microcontrollers with a unipolar power supply. The linearization of the transfer characteristics of the phototransistor allows you to use microcontrollers with low computing power. It was established that the transfer characteristics are closer to linear ones with an increase in the voltage between the collector and the emitter of the phototransistor. The sensor device using the developed transistor was assembled on a PIC16F1713 series microcontroller, which contains an operational amplifier that allows the implementation of a universal synchronous-asynchronous receiver/transmitter digital interface for transmitting the measured light flux data. Implementing a wireless light sensor on the GB2530 module, which is based on the system on a chip CC2530 allows you to get a mobile device. Data exchange on the airwaves takes place in accordance with the IEEE 802.15.4 standard.