Study of 3D-growth conditions for selective area MOVPE of high aspect ratio GaN fins with non-polar vertical sidewalls

Abstract

GaN fins are 3D architectures elongated in one direction parallel to the substrate surface. They have the geometry of walls with a large height to width ratio as well as small footprints. When appropriate symmetry directions of the GaN buffer are used, the sidewalls are formed by non-polar {11-20} planes, making the fins particularly suitable for many device applications like LEDs, FETs, lasers, sensors or waveguides. The influence of growth parameters like temperature, pressure, V/III ratio and total precursor flow on the fin structures is analyzed. Based on these results, a 2-temperature-step-growth was developed, leading to fins with smooth side and top facets, fast vertical growth rates and good homogeneity along their length as well as over different mask patterns. For the core-shell growth of fin LED heterostructures, the 2temperature-step-growth shows much smoother sidewalls and less crystal defects in the InGaN QW and p-GaN shell compared to structures with cores grown in just one step. Electroluminescence spectra of the 2temperature-step-grown fin LED are demonstrated.

Defect-rich GaN interlayer facilitating the annihilation of threading dislocations in polar GaN crystals grown on (0001)-oriented sapphire substrates

“…[20][21][22] In a recent publication, Stanchu et al described the positive effect of compositionally graded AlGaN buried layers in GaN/AlGaN/GaN stacks on the lattice strain relaxation and on the annihilation of TDs. 23 Among the nowadays actively developed techniques which support bending and bunching of the TDs in GaN, the selective area growth (SAG), [24][25][26][27][28] the epitaxial lateral overgrowth (ELO), [29][30][31][32][33] and the facet-controlled epitaxial lateral overgrowth (FACELO) [34][35][36] are to be mentioned.…”

3D GaN Fins as a Versatile Platform for a‐Plane‐Based Devices

“…This optimized growth process, the 2-temperature-step-growth, was reported elsewhere. 20 The most important parameter for a successful three-dimensional (3D) growth is a low V/III ratio (here namely 77). Scanning transmission electron microscopy (STEM) measurements are carried out using a JEOL JEM-2100F equipped with a bright-field (BF) and a high-angle annular dark-field (HAADF) detector.…”

“…Here we introduce GaN microfins as a suitable alternative platform for the application in such devices regarding the rare occurrence of extended defects as well as the availability of nonpolar (and semipolar) crystal planes, which may be capitalized upon in applications such as core-shell LEDs or vertical transistors. 20,21,22…”

Metalorganic chemical vapor deposition of aluminum nitride on vertical surfaces

“…While ALD is known for its excellent conformal coverage, the coverage of MOCVD films on nonplanar features has not been studied. Some experiments have been conducted on the epitaxial lateral overgrowth of AlN [44,45] and GaN [46], and on the selective area growth of GaN [47,48,49]. However, in these studies, the trenches have been only a few micrometers deep and the focus has been on reducing dislocation densities in AlN.…”