Selective area growth (SAG) of InP and GaAs nanostructures has been attempted by metal organic vapour phase epitaxy (MOVPE) [1] and molecular beam epitaxy (MBE) [2], respectively. Here we present the SAG results of InP nanostructure conducted for the first time in a hydride vapour phase epitaxy (HVPE), a near equilibrium process, in which the growth mechanisms and the characteristic features of the grown nanostructures can differ from the far-equilibrium processes, namely MOVPE and MBE.
The nanostructure growth was realized in circular openings provided in a silicon dioxide layer deposited on InP. The samples consisted of triangular arrays of openings with lattice periods ranging from 200 to 640 nm, and the diameter of the opening varied from 130 to 380 nm. For any given period, the diameter of the opening was adjusted so as to keep the fractional area of the openings constant. After growth, the nanostructures were analyzed by atomic force microscopy (AFM) and high resolution scanning electron microscopy (HR-SEM). The results show that the nanostructures were grown selectively inside the openings. The measured heights varied approximately linearly with the diameter of the openings. Interestingly, compared to the growth rate of InP on a planar InP substrate (167 nm/min), the growth rate of the InP nanostructures is exceptionally low. With a growth time of 5 min, the heights of the grown nanostructures were in the 14 to 130 nm range, equivalent to the growth rate of 2.8 to 26 nm/min. The grown structures were to a large degree truncated octagonal in shape, with characteristic stopping planes on top, resembling epitaxial lateral overgrowth conducted on circular openings in the micrometer range. Although we are conducting the growth in HVPE, a high growth rate technique, these stopping planes appear to be the cause of low growth rate in this case. This is interesting since such a faceted surface due to the stopping planes can be specifically sensitized with certain peptides which might be useful in directed nanostructure assembly [3].
References:
1. M. Inari et al., Physica E, vol. 21, pp. 620-624, (2004).
2. T.Toda et al., Physica E, vol. 23, pp. 315-319, (2004).
3. S.R. Whaley, et al., Nature, vol. 405, 665-668, (2000). |