Fabrication and Experimental Characterization of Spin polarized light sources

Information Technology pervades practically every dimension of human existence. Anything that helps the growth of IT, therefore, is of great importance to the general public as well as global technology corporations. This is especially true of semiconductor technology, which lies at the very foundation of IT.

The race to find new ways to make semiconductor electronics more powerful, energy efficient and compact has resulted in the ability to manipulate materials almost down to the atomic level. However, further advances will have to overcome the limitations imposed by the basic nature of the materials when used at the smallest possible dimensions. One way to do this is by finding alternatives to the materials currently in vogue. The other is to delve deeper into the nature and intrinsic behaviour of sub-atomic particles to electric and magnetic fields, which essentially determine the properties of any material.

For long the material of choice in the semiconductor industry, Silicon has become synonymous with it. However, while peerless for several applications, Silicon has proven less than ideal for others such as opto-electronics. Gallium Nitride (GaN) on the other hand has been found to be highly suitable for use in opto-electronics.

The electronics industry has been trying to harness the magnetic properties of material to design and manufacture devices that are more powerful and compact than achieved so far. The resultant technology has been christened spintronics because understanding the spin characteristics of the subatomic particle, electron in a material is essential for understanding and using its magnetic properties. Spintronics has great potential for applications in the opto-electronic industry.

Debashree Banerjee has chosen to combine both these options – Gallium Nitride and spintronics. She has successfully created a semiconductor by inserting small amounts of a magnetic material into Gallium Nitride. Using this combination, she has fabricated a Light Emitting Diode (LED) that emits circularly polarized light.

Little is known at present about the spin characteristics of GaN. The possibility of using GaN in spintronics has not been comprehensively assessed. The work done by Debashree will help bridge this gap. The spin-LED that Debashree has succeeded in fabricating emits light that is circularly-polarised, as a result of the injection of spin into the non-magnetic GaN. This is an important step towards facilitating the use of GaN in a number of applications that can impact areas such as communications, data storage and quantum computing.

About the work that she has been doing, she says “I have always been curious about physical phenomena and the reasons behind materials behaving the way they do. It is also very rewarding to put my knowledge of the laws of physics to use in designing innovative gadgets. What I am doing now combines both of these”.

For Debashree, the most rewarding part would be creating a transistor that combines both memory and logic functions using the understanding of spin characteristics gained from her research. While that goal is still a distant dream, the journey itself is fascinating enough to be its own reward.

A research scholar at the IITB-Monash Research Academy in Mumbai, Debashree has been working under the guidance of Prof. Dipankar Saha and Prof. Swarup Ganguly of IITB and Prof. Zhe Liu of Monash University.

The IITB-Monash Research Academy is a Joint Venture between the IIT Bombay, India and Monash University, Australia. Opened in 2008, the IITB-Monash Research Academy operates a graduate research program located in Mumbai that aims at enhancing research collaborations between Australia and India. Students study for a dually-badged PhD from both institutions, and spend time during their research in both India and Australia.

Research scholar: Debashree Banerjee, IITB-Monash Research Academy

Project title: Fabrication and Experimental Characterization of Spin polarized light sources

Supervisors: Prof. Dipankar Saha, Prof. Swaroop Ganguly, Prof. Zhe Liu

Contact details: debashreeb@ee.iitb.ac.in

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