Based on a virtual GaN substrate approach on Si(111) by a step graded double oxide (Sc2O3/Y2O3) buffer, we report a “proof of principle” study on the enhanced photo-response of ultraviolet GaN photo-detectors due to embedded DBRs (distributed Bragg reflectors). Embedded DBRs benefit from an order of magnitude lower number of superlattice sequences in contrast to III- nitride systems due to the high refractive index contrast between high-k Y2O3 and low-k Si. The UV (ultraviolet) reflectance efficiency of the designed DBR is proven by a considerable photo-response increase in the UV range in comparison to reference GaN layers on Si(111) without DBRs.

Based on a novel double step oxide buffer heterostructure approach for GaN integration on Si, we present an optimized Metal-Semiconductor-Metal (MSM)-based Ultraviolet (UV) GaN photodetector system with integrated short-period (oxide/Si) Distributed Bragg Reflector (DBR) and leakage suppressing Metal-Oxide-Semiconductor (MOS) electrode contacts. In terms of structural properties, it is demonstrated by in-situ reflection high energy electron diffraction and transmission electron microscopy-energy dispersive x-ray studies that the DBR heterostructure layers grow with high thickness homogeneity and sharp interface structures sufficient for UV applications; only minor Si diffusion into the Y2O3 films is detected under the applied thermal growth budget. As revealed by comparative high resolution x-ray diffraction studies on GaN/oxide buffer/Si systems with and without DBR systems, the final GaN layer structure quality is not significantly influenced by the growth of the integrated DBR heterostructure. In terms of optoelectronic properties, it is demonstrated that—with respect to the basic GaN/oxide/Si system without DBR—the insertion of (a) the DBR heterostructures and (b) dark current suppressing MOS contacts enhances the photoresponsivity below the GaN band-gap related UV cut-off energy by almost up to two orders of magnitude. Given the in-situ oxide passivation capability of grown GaN surfaces and the one order of magnitude lower number of superlattice layers in case of higher refractive index contrast (oxide/Si) systems with respect to classical III-N DBR superlattices, virtual GaN substrates on Si via functional oxide buffer systems are thus a promising robust approach for future GaN-based UV detector technologies.

We report the growth of thin ScN layers deposited by plasma-assisted molecular beam epitaxy on Sc2O3/Y2O3/Si(111) substrates. Using x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we find that ScN films grown at 600 degrees C are single crystalline, twin-free with rock-salt crystal structure, and exhibit a direct optical band gap of 2.2 eV. A high degree of crystalline perfection and a very good lattice matching between ScN and GaN (misfit < 0.1%) makes the ScN/Sc2O3/Y2O3 buffer system a very promising template for the growth of high quality GaN layers on silicon

A comparative study of thin aluminum nitride (AlN) films deposited by plasma-enhanced atomic layer deposition in the SENTECH SI ALD LL system applying either a direct inductively coupled plasma (ICP) or an indirect capacitively coupled plasma (CCP) source is presented. The films prepared with the ICP source (based on a planar triple spiral antenna) exhibit improved properties concerning the growth rate per cycle, total cycle duration, homogeneity, refractive index, fixed and mobile electrical charges, and residual oxygen content compared to the CCP source, where the comparison is based on the applied plasma power of 200 W. The increase of the plasma power to 600 W in the ICP process significantly reduces the residual oxygen content and enhances the electrical breakdown field. The AlN layers grown under these conditions, with a growth rate per cycle of 1.54 Å/cycle, contain residual oxygen and carbon concentrations of about 10% and 4%, respectively, and possess a refractive index of 2.07 (at 632.8 nm).

Epitaxial growth of atomically-sharp interfaces serves as one of the main building blocks of nanofabrication. Such interfaces are crucial for the operation of various devices including transistors, photo-voltaic cells, and memory components. In order to avoid charge traps that may hamper the operation of such devices, it is critical for the layers to be atomically-sharp. Fabrication of atomically sharp interfaces normally requires ultra-high vacuum techniques and high substrate temperatures. We present here a new self-limiting wet chemical process for deposition of epitaxial layers from alkoxide precursors. This method is fast, cheap, and yields perfect interfaces as we validate by various analysis techniques. It allows the design of heterostructures with half-unit cell resolution. We demonstrate our method by designing hole-type oxide interfaces SrTiO3/BaO/LaAlO3. We show that transport through this interface exhibits properties of mixed electron-hole contributions with hole mobility exceeding that of electrons. Our method and results are an important step forward towards a controllable design of a p-type oxide interface. Growth methods of epitaxial thin films can be roughly categorized as physical and chemical. While physical methods (i.e. molecular beam epitaxy, pulsed laser de-position (PLD)[1]) are based on creating a beam of the film material and transporting it in vacuum onto the sub-strate. Chemical methods such as: chemical vapor depo-sition and atomic layer deposition (ALD) use a chemical precursor, a compound containing the film growth material. The precursor is transferred in vacuum onto the substrate, where the surface catalyzes the precursor dis-sociation reaction, and the deposition of the film. While giving very good results for film growth, these methods lack the versatility and become increasingly complex [2] when a wide variety of surface monolayers is required. (A) (B) (C) FIG. 1: Solution monolayer epitaxy process. The TiO2 terminated SrTiO3 is submersed in a solution of Ba II iso-propoxide (A) in ethylene glycol, which is kept slightly below the decomposition temperature of the precursor Ba II iso-propoxide. Surface catalysis results in decomposition of of the precursor, which results in epitaxial deposition of BaO on the surface (B). This process is terminated when a complete layer of BaO covers the surface (C). FIG. 2: (color online). Two models of SrTiO3/LaAlO3 interfaces. On the right the conventional n-type interface. On the left our new p-type interface which incorporates a mono-layer of BaO between the SrTiO3 substrate and the polar LaAlO3 film. The presence of the Ba film forces a growth with inverted LaAlO3 polarity. In Solution monolayer epitaxy (SoME) the substrate of choice, in this case a (100) TiO 2 terminated SrTiO 3 , is submersed in a solution of a dissolved precursor of choice, at a temperature slightly lower than its decomposition temperature. Under these conditions the precursor molecules do not decompose in the solution unless they are in close proximity to the surface ...