Directed Matrix Seeding of Nitride Semiconductor Nanocrystals

The controlled formation of semiconductor nanocomposites offers a unique opportunity to tailor functional materials with a variety of novel properties. A promising approach to nanocomposite synthesis is matrix-seeded growth, which involves ion-beam-amorphization of a semiconductor film, followed by nanoscale re-crystallization via annealing. In this work, we are studying the formation and evolution of N ion-implanted InAs and GaAs (InAs:N, GaAs:N). The InAs:N and GaAs:N nanocomposites are synthesized using 100keV ion-implantation with a dose of 5x10$^{17}$cm$^{-2}$, at 77K and 300C, respectively. In all cases, the as-implanted structures are primarily amorphous, and after appropriate rapid thermal annealing (RTA) sequences, zincblende (ZB) InN and GaN [1] nanocrystals are formed. We are also developing a novel approach to \textit{direct} the seeding of nanostructure arrays, using a combination of focused-ion-beam (FIB) implantation in combination with conventional ion implantation. To date, we have demonstrated the selective positioning of wurtzite (WZ) and ZB GaN nanocrystals using 75keV and 100keV N implantation, followed by FIB patterning and 800C RTA. The growth mechanisms and structural evolution of nitride crystallites will also be discussed. [1] X. Weng, et al, \textit{J. Appl. Phys}., \textbf{92} 4012 (2002)