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Development of Rocksalt Semiconductors

Semiconductors are part and parcel of modern electronic devices and they have revolutionized the modern world dominated by Information technology. While Silicon (Si) is most commonly used semiconductor for a long time, Germanium (Ge), Gallium Arsenide (GaAs), Indium Phosphide (InP), Alumnum Nitride (AlN) and various others semiconductors are also studied extensively over last five decades and many of them have already found applications. One thing that is common among all these well-known semiconductors is that all of them have non-cubic crystal structure. While Si and Ge have diamond crystal structure, common arsenides and phosphides like GaAs and InP have zinc blende structure. Nitride semiconductors like AlN and GaN which have found applications in LED and other optoelectronic devices have wurtzite crystal structure. However if we turn our attention to metals, we find that most commonly used metals like Cu, Al, Fe and others have cubic crystal structure. Thus there is a mismatch in the crystal structure between the important semiconductors and metals. This mismatch prevents us from integrating them efficiently in a device thus limiting their performances. To overcome this great challenge, we are interested in exploring rocksalt cubic nitride semiconductors that are compatible with other cubic metals.

Over the span of last few years, we have developed three such rocksalt semiconductors. (a) Scandium Nitride (ScN), (b) Yittrium Nitride (YN) and more recently (c) (Al,Sc)N. Our work on ScN (both experimental and modeling) has uncovered many important aspects of its electronic, optical, and thermoelectric properties. Our modeling results of YN have also opened up a new avenue of research for this material. More recently we are exploring rocksalt phase of (Al,Sc)N which in many sense will expand the horizon of these rocksalt semiconductors.



1. Electronic Structures, Phonons and Thermal Properties of ScN, ZrN and HfN: A first-principles Study: B. Saha, J. Acharya, T. D. Sands and UU V. Waghmare. Journal of Applied Physics 107, 033715 (2010).

2. Electronic structure, vibrational spectrum, and thermal properties of yttrium nitride (YN): A first-principles study: B. Saha, T. D. Sands and U. V. Waghmare. Journal of Applied Physics  109, 083717 (2011).

3. High mobility and high thermoelectric power factor in epitaxial ScN films deposited by reactive magnetron sputtering onto MgO(001) substrate. P. V. Burmistrova, J. Maassen, T. Favaloro, B. Saha, S. Salamat, Y. R. Koh, M. S. Lundstrom, A. Shakouri, and T. D. Sands. Journal of Applied Physics 113, 153704 (2013).

4. Electrical and Optical Properties of ScN and Mn-doped ScN deposited by dc-magnetron sputtering. B. Saha, G. Naik, V. Drachev, A. Boltasseva, E. E. Marinero, and T. D. Sands. J. Appl. Phys., 114, 063519 (2013)

5. B. Saha, S. Saber, G. V. Naik, A. Boltasseva, E. Stach, E. P. Kvam, and T. D. Sands, “Development of epitaxial AlxSc1-xN for artificially structured metal/semiconductor superlattice metamaterials.” Phys. Stat. Sol. B, 252, 251 (2015). (Editor’s Choice and Cover Article, Purdue MSE News)

Collaborators: Sammy Saber (Purdue), Gururaj Naik (Purdue), Prof. Eric Stach (Brookhaven National Lab.), Prof. Eric Kvam (Purdue), Alexandra Boltasseva (Purdue).