Growth mechanism of catalyst‐free [0001] GaN and AlN nanowires on Si by molecular beam epitaxy

Abstract

Real‐time in‐situ X‐rays scattering experiments were performed to study the nucleation process of GaN nanowires grown by plasma‐assisted molecular beam epitaxy on AlN(0001)/Si(111). From the comparison between the case of nanowires and the case of GaN quantum dots, it is concluded that nanowire precursor islands are completely relaxed from the beginning. Next, based on high resolution electron microscopy analysis, it is demonstrated that relaxation of nanowire precursors is associated to formation of dislocations at the AlN/GaN interface, establishing that three‐dimensional islanding and plastic strain relaxation of GaN are two necessary conditions for nanowire growth. Along the same lines, we demonstrate that three‐dimensional islanding of AlN on SiO2 leads to formation of AlN nanowires with structural and optical properties characteristic of high quality relaxed material (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Selective Area Growth and Structural Characterization of GaN Nanostructures on Si(111) Substrates

“…It can also be seen that while some of the nuclei grew together, most did not, because strain caused by the very large lattice mismatch limited the lateral growth of the nuclei. In other words, strain, which aids self-assembly of GaN nanowires by limiting lateral growth [16][17][18][19][20][21], detracts from selective area NW growth. Reducing the in-plane mismatch by an order of magnitude, from 2.3% for sample N-Al to 0.2% for sample N-AlGa, increased the hole fill-factor, as can be seen in Figure 1c,d.…”

“…Bragg peak positions were determined by parabolic fitting of omega-2theta scans. The c-lattice parameters were calculated from the symmetric (0002) (0004) (0006) peaks and then used to determine a-lattice parameters from the asymmetric (10-14) (10)(11)(12)(13)(14)(15) and (20)(21)(22)(23)(24) peaks [8]. The a-lattice parameters and their errors, reported in Table 1, are the average of the values determined from the three asymmetric peaks and their standard deviation respectively.…”

“…1 Sample polarity was verified by STEM ABF imaging. 2 Calculated by fitting (0002) (0004) (0006) (10-14) (10)(11)(12)(13)(14)(15) and (20)(21)(22)(23)(24) XRD Bragg peaks; the error is the standard deviation of the a o values determined from the three asymmetric peaks. 3 Mismatch was calculated as described in the text, assuming a relaxed GaN a o of 0.3189 nm.…”

GaN based nanorods for solid state lighting

“…33,36 Furthermore, Consonni et al free energy which explains the transition from GaN nanotruncated pyramidal structure to vertical nanorod growth. 37 They observed several consecutive shape transitions from spherical caps through truncated-to full-pyramid-shaped islands at the onset of the nucleation process (shown in Fig.…”