Self-Assembled GaN Nanowires on Diamond

Abstract

We demonstrate the nucleation of self-assembled, epitaxial GaN nanowires (NWs) on (111) single-crystalline diamond without using a catalyst or buffer layer. The NWs show an excellent crystalline quality of the wurtzite crystal structure with m-plane faceting, a low defect density, and axial growth along the c-axis with N-face polarity, as shown by aberration corrected annular bright-field scanning transmission electron microscopy. X-ray diffraction confirms single domain growth with an in-plane epitaxial relationship of (10 ̅10)(GaN) [parallel] (01 ̅1)(Diamond) as well as some biaxial tensile strain induced by thermal expansion mismatch. In photoluminescence, a strong and sharp excitonic emission reveals excellent optical properties superior to state-of-the-art GaN NWs on silicon substrates. In combination with the high-quality diamond/NW interface, confirmed by high-resolution transmission electron microscopy measurements, these results underline the potential of p-type diamond/n-type nitride heterojunctions for efficient UV optoelectronic devices.

Surface passivation and self-regulated shell growth in selective area-grown GaN–(Al,Ga)N core–shell nanowires

“…Both FFT patterns show the typical wurtzite pattern. 18 However, a clear broadening in both directions, i.e.…”

GaN nanowires on diamond

“…The NWs are separated from each other and free-standing on the bare diamond substrate, without the appearance of a matrix layer. The growth mechanism is governed by a statistical nucleation process without involving a catalyst (non-vapor liquid solid), resulting in an arbitrary distribution of the individual nuclei on the surface [17,18]. Similar to the growth on silicon (111) an incubation time of about 20-40 min is observed which additionally promotes the variation of individual NW dimensions [19,20].…”

“…5a a cross-sectional aberration-corrected high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) image of a single self-assembled GaN NW on a (111) diamond substrate is shown [17]. To investigate a potential interdiffusion of substrate material into the NW bases electron energy loss spectroscopy (EELS) images are included in false colors for the atomic species Ga, N and C. An incorporation of C could be problematic for device structures since it is known to be an amphoteric dopant in GaN [28][29][30].…”

“…To investigate a potential interdiffusion of substrate material into the NW bases electron energy loss spectroscopy (EELS) images are included in false colors for the atomic species Ga, N and C. An incorporation of C could be problematic for device structures since it is known to be an amphoteric dopant in GaN [28][29][30]. However, no significant amount of C from the diamond substrate into the GaN NWs has been detected, which is a consequence of the high chemical inertness of diamond and in contrast to the substantial interdiffusion of substrate material observed for silicon substrates [17,19]. This has also been confirmed by photoluminescence measurements under backside excitation of the NWs, i.e.…”

Nanoscale conductive pattern of the homoepitaxial AlGaN/GaN transistor

“…Blue, white, and blueviolet light-emitting diodes are all based upon GaN semiconductors, providing a wide range of color reproduction in liquid crystal display panels of mobile phones and in a myriad of other smart lighting applications [2]. Furthermore, with naturally enhanced light extraction geometry engineered at the nanoscale, GaN based nano-structures are ideally suited for nanophotonics and optoelectronics [3][4][5]. Within onedimensional heterostructures, one may also expect an electron gas at the core/shell interface in a similar fashion to what happens in planar AlGaN/GaN heterojunctions [6].…”