Scientists from the Jawaharlal Nehru Center for Advanced Scientific Research (JNCASR), an autonomous institute under the Department of Science and Technology, have manufactured an economical and energy-efficient wafer-scale (thin-slice) photo detector with gold-silicon interface, for security applications. It can help detect weakly scattered light as an indication of unwanted activity.
Photo detectors are at the heart of any optoelectronic circuit that can detect light and are used for a wide variety of applications, from controlling automatic lighting in supermarkets to detecting outer galaxy radiation and security-related applications. However, the material costs and the complicated manufacturing processes involved in realizing high-quality detectors make them prohibitive for everyday applications.
The invention of JNCASR scientists, which was published in the journal Applied Electronic Materials of the American Chemical Society, provides a simple and cost-effective solution-oriented manufacturing method for high-quality photo detector.
The scientists fabricated a gold (Au) – silicon (n-Si) interface, which showed a high sensitivity to light and demonstrated the photo-detecting action. The Au-Si interface has been established by galvanic deposition, a metal electroplating technique that uses water-based solutions (electrolytes), which contain the metals to be deposited as ions. In addition, a nanostructured Au film was also deposited on p-type silicide (with an excess of positive charges), which functions as a charge collector.
Being a solution-based technique, the method is very economical and allows the fabrication of large areas without compromising the detector response. The process is quick and only takes a few minutes to fabricate a detector from any area. The metal nanostructures improved the performance of the fabricated detector by capturing the incident light. This photo detector exhibited long-term environmental stability.
The detector has a fast response of 40 microseconds and can detect low light intensities. The device covers a wide spectrum from ultraviolet to infrared. In addition, it exhibits excellent uniformity across the entire active region with less than 5% variation in response. In particular, the detector operates in self-powered mode, which means that the device does not require an external power supply for its operation, making it energy efficient. With a widely available protective coating, excellent environmental stability is shown for several days under the harsh conditions. The scientists also demonstrated the utility of the photodetector as a prototype imaging system, lux and power meter, and also as a tool for security applications.
(With inputs from PIB)