Formation mechanisms of GaN nanorods grown on Si(111) substrates

Growth Mechanism of Catalyst-Free and Mask-Free Heteroepitaxial GaN Submicrometer- and Micrometer-Sized Rods under Biaxial Strain: Variation of Surface Energy and Adatom Kinetics

“…GaN submicrometer- and micrometer-sized rods (SMRs) are some of the most promising structures for high performance optoelectronic devices, such as light emitting diodes (LEDs), , lasers, , and solar cells, due to their high quantum efficiency and high surface to volume ratio. However, it is not easy to grow GaN SMRs with a high aspect ratio without the assistance of a metal catalyst, , a patterning mask, ,, or a doping constituent, as a result of the long lateral diffusion length of adatom on the top surface of GaN that leads to the energetically favored thermodynamic equilibrium shape, especially at the high growth temperatures (>1000 °C) and the high V/III precursor molar ratio of metal–organic chemical vapor deposition (MOCVD), contrary to molecular beam epitaxy ,, or hydride vapor phase epitaxy, which can grow the vertically well-oriented GaN SMRs without difficulties. Nevertheless, in the case of the vapor–liquid–solid (VLS), metal catalysts, such as Au or Ni, may act as impurities and GaN SMRs produced in this manner are not vertically aligned well.…”

Effect of gas-mixing and substrate temperatures on structural properties of GaN nanorods grown on Si (1 1 1) substrates by using hydride vapor-phase epitaxy

“…Because they have novel physical properties of large band gaps, large exciton binding energies, and excellent chemical stabilities [1][2][3][4], optoelectronic devices fabricated utilizing one-dimensional (1-D) nanostructures, such as nanowires and nanorods, have exhibited enhanced light extraction efficiency and quantum efficiency in comparison with devices consisting of planar structures [5][6][7]. GaN/Si heterostructures, which are fabricated by utilizing the combined advantages of the large excitonic binding energy of GaN nanorods and the availability of low-cost and large-area Si substrates, are particularly interesting due to their potential applications in promising nanodevices operating at relatively low power consumption [8].…”

“…Some GaN islands during the initial formation stage have insufficient time to obtain stable positions along the [0 0 0 1] GaN growth direction perpendicular to the Si (111) substrate due to the fast growth rate of GaN nanorods grown by using the HVPE method[4]. The XRD results show that the morphologies of GaN nanorods, such as their diameter, can be controlled by changing the T 3 .Fig.…”

Picosecond Carrier Recombination of Single-Crystalline GaN Nanorods Grown on Si(111) Substrates

“…The GaN nanorods grown by HVPE on Si substrates have been shown to have crystalline structures with very few defects. 6,7) However, few studies on the optical properties of the HVPE-grown GaN nanorods have been reported. In this paper, we report a time-resolved photoluminescence (PL) study of 1D GaN nanorods with c-axis-oriented single-crystalline wurtzite structures.…”

“…The GaN nanorods used in this study were grown on Si(111) substrates without a catalyst by an improved HVPE method using a reaction chamber that was divided into three reaction zones. 6,7) The carrier concentration of the P-doped n-Si substrate with (111) orientation used in this experiment was 1 Â 10 15 cm À3 . The Ga source was reacted with HCl and N 2 carrier gases at 850 C. The Ga metal was converted into gallium chloride (GaCl x ) during the reaction.…”