From UPSC perspective, the following things are important :
Prelims level : Photodetectors and their applications
Mains level : NA
Indian scientists have fabricated an economical and energy-efficient wafer-scale photodetector using gold – silicon interface, for security applications.
A basic question on the working principle of Photodetectors can be asked in the Prelims.
What are Photodetectors?
- Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation.
- A photodetector has a p–n (positive-negative) junction that converts light photons into the current.
- The absorbed photons make electron-hole pairs in the depletion region.
- Photodiodes and phototransistors are a few examples of photodetectors. Solar cells convert some of the light energy absorbed into electrical energy.
- The material cost and the intricate fabrication processes involved in realizing high-performance detectors make them unaffordable for day to day applications.
- Photodetectors are the heart of any optoelectronic circuit that can detect light.
- They are employed for a wide variety of applications ranging from controlling automatic lighting in supermarkets to detecting radiation from the outer galaxy as well as security-related applications.
- They range from simple devices that automatically open supermarket doors, to receivers on the TV remote controls.
What did Indian researchers achieve?
- The scientists have fabricated gold (Au) – silicon (Si) interface, which showed high sensitivity towards light demonstrating the photodetection action.
- The Au–Si interface was brought about by galvanic deposition, a technique for electroplating of metals, wherein water-based solutions (electrolytes) are used, which contain the metals to be deposited as ions.
- In addition, a nanostructured Au film also was deposited on top of p-type silicide (having an excess of positive charges), which acts as a charge collector.
- Being a solution-based technique, the method is highly economical and enabled large-area fabrication without compromising the detector response.
- The process is quick, taking only minutes to fabricate a detector of any arbitrary area and exhibited a rapid response of 40 microseconds.
- This photodetector displayed long-term environmental stability.
- The Indian invention provides a simple and cost-effective solution-based fabrication method for high-performance photodetector.
- It could help detect weak scattered light as an indication of unwanted activity.