Pallab Banerji

Indian Institute of Technology, Kharagpur, India

Title: Gallium nano droplet catalyzed growth of ternary nanowires

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Biography

Dr. P. Banerji is a Professor in Materials Science in Indian Institute of Technology Kharagpur, India. His area of specialization is semiconductor materials and low dimensional systems for various applications in the field of thermoelectrics and optoelectronics. Prof. Banerji supervised twenty-five doctoral students and several Masters theses. He has published around 150 research papers in peer reviewed journals. Prof. Banerji is a recipient of MRSI medal instituted by the Materials Research Society of India.

Dr. Sisir Chowdhury is a member of the faculty in Physics in Midnapore College (Autonomous). He is a specialist in MOCVD growth and completed his Ph.D. under the supervision of Prof. P. Banerji.

Abstract

Gallium (Ga) nano droplets were deposited on silicon (Si) substrate by pyrolysis of tri-methyl gallium (TMGa) for the self-assisted growth of InGaAs nanowires via vapor solid liquid technique using metal organic chemical vapor deposition (MOCVD) system. Group V hydride such as arsine, and group III alkyls, viz. TMGa and tri-methyl indium were used as precursors. It was observed that at a temperature of 450 0C, the growth rate is very small, whereas it is very high at 550 0C due to higher cracking efficiency of TMGa. At an intermediate temperature of 550 0C, Ga droplets are found uniform throughout the substrate with an average diameter of 27 nm and a density of 2.8 x 109 cm-2. The effect of growth temperature and duration on the shape and size of the droplets were demonstrated on the basis of Oswald ripening based coalescence mechanism. It was found that partial coalescence of smaller droplets leads to the formation of valve-shaped nanostructures whereas complete coalescence of droplets gives rise to spherical nanomorphology. Self-catalyzed InGaAs nanowires were grown on Si substrate by a two steps process in MOCVD using Ga nano droplets as catalyst. Growth temperature and V/III ratio were optimized to obtain vertically stranded nanowires. Growth morphology showed that with increasing V/III ratio, the diameter of the nanowires decreases. It was also found that the indium and gallium fraction varies along the length of the grown nanowires. The TEM fringe pattern revealed that the nanowires were grown along the (111) direction.