This work studies application and development of technological solutions for the formation of nano-templates for heterostructures of III-nitrides, including those with nonpolar crystallographic orientation, in order to ensure a low density of defects and the possibility of obtaining nanostructures (nanorods, quantum dots, etc.) for their practical implementation in optoelectronic integrated circuits.
The the approach to defect nucleation modeling in three-dimensional confined nanoislands of templated nanostructures was considered in order to ensure a low density of dislocation of heterostructures.
It is determined that the developed nano-templates of anodized aluminum oxide formed in a solution of 0,05M oxalic acid can provide satisfactory homogeneity and periodicity of pores, and the statistical distribution of their diameters over the surface area, as established by atomic force microscope, is characterized by a bimodality: their predominant number was determined by diameters of ~ 20-30 nm or 55-100 nm, which, according to the proposed simplified mathematical model, may provide expediency for considering such nano-templates in experiments to ensure for low dislocation density and controllable size and location of nanostructures.
It was investigated and proved the possibility of using on the silicon anodic alumina nano-templates, optimal according to the simplified mathematical model of the defect generation process, for growth by the method of chloride-hydride gas-phase epitaxy of non-polar α-GaN with crystallographic orientation (112 ̅0) and low stacking fault defect density, compared with results on the basis of methods of one-stage lateral growth or using buffer layers on sapphire and silicon carbide, respectively.
The technological process, which is not lithographic, is investigated and developed in relation to the formation of nonpolar nano-heterostructures of III-nitrides with low defect density and the ability to control the size and location (nanowires, nanoclusters and quantum dots) on the basis of the transfer of a picture from hexagonal nano pores from anodized oxide templates aluminum on a SiO2 mask. In a study by the method of translucent electron microscopy, it was determined that the cross sections of GaN nanorods have vertical side walls, cone-shaped frame, and their height is determined by the thickness of the SiO2 mask, and the density of the dislocations at the same time is ~ 3x106 cm-2.
However, for the MOCVD epitaxy (horizontal reactor, EPIQUIP equipment), thermodynamic parameters (temperature, pressure) and precursors were experimentally determined, in which nanopores with a radius of <10 nm were formed on the sapphire surface. It was shown that It was possible to grow heteroepitaxial layers of III-nitrides with a low density of dislocations, as well as to form consolidated phases of nanocarbides encapsulated in the atomic structure of aluminum or boron carbonitride on the obtained templates of nanotexted sapphire in one technological cycle.
The application of the obtained nano-templates of textured sapphire was considered for UV photodiodes and energy storage layers that can be used in optoelectronic integrated circuits for space, biological and military purposes due to the high thermal, chemical and radiation resistance of both sapphire and III-nitrides, where the traditional silicon does not fit.
It was obtained low dislocation density (~ 5x106 cm -2) comparable to structures formed by the method using epitaxial lateral overgrowth for GaN layers formed on such nano-templates of textured sapphire. The dislocation density was determined on the basis of the diffusion length of nonequilibrium carriers through the electron-beam-induced current method.
For UV GaN photodiodes with Schottky barrier, it is shown that the structures formed on nano-templates of textured sapphire, in comparison with photodiodes without nano-templates, provide a steeper long-wave (375-475 nm) edge of normalized photosensitivity, decreasing it by an order of magnitude in this range , which allows to handle without special filters.
For energy accumulation layers, in one МОСVD technological cycle on the textured sapphire nano-templates, it was proposed to form nano-carbides, consolidated AlCN or BСN phases in a stream of trimethyl aluminum or triethyl boron, respectively, as well as layers of hexagonal boron nitride (h-BN), in which graphene can be encapsulated.
Keywords: nanotemplate, heterostructures, nitrides of the III group, little defect, anodized aluminum oxide, photodetectors.
