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.

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.

Benefits

• 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.

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