V. V. Mamedov

Thermally stable, highly conductive, and transparent ZnO layers prepared in situ by chemical vapor deposition

Abstract It is possible to fabricate thin epitaxial ZnO layers doped in situ with In and Ga impurities by chemical vapor deposition (CVD) in a low-pressure system. Highly conductive and transparent ZnO:Me (0.1–2 wt.%) films are deposited on (1012) sapphire substrates. Electrical, optical, and structural properties of the films are investigated. The ZnO:Me thin epitaxial layers (TEL) features unique thermal stability of their electric properties to thermocyclings within the 300–950 K temperature range in various ambient. It is found that the crystal structure perfection must be among the main factors conditioning the thermal stability of the films. It is suggested a formation of metal cluster structures-whiskers over the doped film surface.

Zinc oxide whiskers

This paper describes the first experiments on the production of zinc oxide whiskers in air without crystallization chambers or reactors, using CO2-laser radiation. The features of their exciton luminescence are studied, and they are compared with bulk single crystals and epitaxial layers of Zno.

On exciton luminescence of ZnO/Al2O3 epitaxial thin films

Abstract Exciton luminescence of non-doped and newly prepared gallium-doped ZnO epitaxial thin films deposited onto sapphire substrates in a low-pressure system within a single chemical vapor deposition cycle is studied depending on films thickness as well as the doping degree. It is shown that the thickness dependence of the ratio between the integral intensities of single-phonon and double-phonon lines allows one to estimate the transition layer thickness.

Epitaxial ZnO films on non-crystalline substrates

First results on a preparation of epitaxial ZnO films on non-crystalline substrates are presented. A two-step method is proposed to fabricate the single-crystalline ZnO films on non-crystalline substrates (alumina and fused silica). To secure the further autoepitaxy, a thin intermediate basis-oriented textured ZnO layer was deposited by a dc magnetron sputtering, as the first step. The epitaxial films prepared by CVD technique on the substrate with the buffer layer in the low pressure system feature high structural quality and smooth surface while the films prepared onto a clear substrate surface were polycrystalline.

Fabrication and properties of an n-ZnO:Ga/p-GaN:Mg/α-Al2O3 heterojunction

The first results of growing ZnO/GaN/α-Al2O3 heteroepitaxial structures in a low-pressure flow-through reactor using chemical-vapor deposition and stimulation with a plasma of radio-frequency discharge are reported. Activation of reactants in the course of growth made it possible to significantly increase the effective pressure of atomic oxygen in the reactor, considerably reduce the temperature of epitaxy, improve the morphological and structural parameters of ZnO layers, and form a n-ZnO:Ga/p-GaN:Mg/α-Al2O3 heterojunction.

Method for manufacturing zinc oxide nanowhisker arrays

Arrays of zinc oxide (ZnO) nanowhskers oriented perpendicularly to the surface of a substrate have been obtained by explosive laser evaporation of ZnO target on (0001)-oriented sapphire and unoriented silica, glass ceramic composite (Polycor), and glass substrates with magnetron-deposited ZnO sublayers layers. X-ray diffractograms of the nanowhisker arrays have been measured and features of their exciton luminescence have been studied.

ZnO-based metal-insulator-semiconductor UV light-emitting diodes prepared by ion implantation

In this paper, we describe the N/sup +/-ion implantation of Ga doped ZnO films grown by chemical vapor deposition on a sapphire substrate. Depositing an appropriate metal onto this system can create a metal-insulator-semiconductor (MIS) type diode. Such ZnO-based MIS diodes, and their emission properties are discussed. The ohmic contact, to the lower conducting ZnO insulating layer, is made by indium. Current-voltage measurements shows good, rectifying diode-like behavior, with a threshold voltage near 3 V, and a reverse current of about 10/sup -6/ A. Under forward bias, ultraviolet emission is observed at room temperature (RT), with a wavelength maximum at /spl sim/388 m (/spl sim/3.197 eV).

On the possibility of ZnO-based quasi-bicrystal structure preparation

We present the first results of the two-step growth of the quasi-bicrystal structures containing interblock boundaries in epitaxial zinc oxide layers on α-sapphire. Using the intermediate buffer layer technique we have successfully prepared highly oriented layers of (110)ZnO and (0001)ZnO with clearly pronounced boundaries between blocks on the same (102)Al2O3 substrate surface. The high quality of the quasi-bicrystal structures was confirmed by x-ray diffraction and reflected high-energy electron diffraction measurements.

Synthesis of epitaxial layers of zinc oxide on nonorienting substrates

The first experiments on the growth of single-crystal layers of zinc oxide on nonorienting substrates (crystalline leucosapphire and fused quartz) by chemical transport reactions in a reduced-pressure flow-through reactor in a hydrogen atmosphere is reported. To ensure autoepitaxy on a surface of a nonorienting substrate, an optimized intermediate layer of zinc oxide of thickness 200–1000 Å, which provides a texture of basal orientation regardless of the orienting properties of the substrate, is preliminarily deposited by magnetron sputtering. It is shown that the subsequent growth of layers on such a surface by a chemical transport reaction to a thickness of 1–5 ensures high structural perfection, uniformity, and a very smooth surface, while polycrystalline films are deposited on the portion of the surface without a buffer layer. The proposed method can be used to grow heteroepitaxial structures and other electronic materials on nonorienting substrates using chemical transport reactions.

High-quality ZnO/GaN/α-Al2O3 heteroepitaxial structures grown by CVD

The first results on the preparation of (0001)ZnO/(0001)GaN/(0001) α-Al2O3 heteroepitaxial structures by CVD in a low-pressure flow-type reactor are reported. Study of the surface morphology and X-ray diffraction patterns showed high structural perfection of the zinc oxide layer, with a block misorientation in the basal plane not exceeding 21′. The photoluminescence spectra of samples exhibited dominating emission in the exciton region.