Nanocrystal Formation in Ion-Beam Synthesized GaAs:N and InAs:N

Ion-implantation followed by thermal annealing offers a unique approach to custom tailoring of semiconductor nanocomposites. For N ion-implanted GaAs (GaAs:N), an amorphous layer with crystalline GaAs remnants is often observed. Subsequent furnace or rapid-thermal annealing (RTA) leads to the formation of zincblende (ZB) GaN nanocrystals [1], which transform to wurtzite (WZ) following extended furnace annealing [2]. For N ion-implanted InAs (InAs:N), nanocrystal formation and evolution has not been previously reported. We are studying the formation and evolution of GaAs:N and InAs:N nanocomposites, synthesized using 100keV ion-implantation with a dose of 5x10$^{17}$cm$^{-2}$, at 300C and 77K. In all cases, the as-implanted structures are primarily amorphous. For GaAs:N, RTA up to 625C leads to an amorphous layer with crystalline GaAs remnants, while RTA in the range 675-700C results in both ZB and WZ nanocrystallites. For InAs:N, 500C RTA leads to the formation of ZB InN-rich and InAs-rich nanocrystals, with amorphous matrices and domains. We will discuss the role of crystalline remnants in the nucleation and growth of ZB nanocrystals, and the mechanisms of the ZB-WZ transformation. [1] X. Weng, et al, \textit{J. Appl. Phys}., \textbf{92} 4012 (2002) [2] X. W. Lin, et al, \textit{Appl. Phys. Lett}. \textbf{67}, 2699 (1995)