CBE growth of high‐quality ZnO epitaxial layers

Abstract

Further improvements on the recently reported novel approach to zinc oxide Chemical Beam Epitaxy (CBE) are presented. Hydrogen peroxide is employed as a very efficient novel oxidant. ZnO layers with a thickness from 100 nm to 600 nm were grown on c-sapphire using a MgO buffer. PL-mapping as well as conductivity mapping shows a good uniformity across the 2 inch ZnO-on-sapphire epiwafers. The measured surface roughness for the best layers is as low as 0.26 nm. HRXRD measurements of the obtained ZnO layers show excellent quality of the single crystalline ZnO. The FWHM of the HRXRD (0002) rocking curves measured for the 2 inch ZnO-on-sapphire wafers is as low as 27 arcsec with a very high lateral homogeneity across the whole wafer. Plane view HRTEM observations reveal the very good quality of the ZnO films. The results indicate that CBE is a suitable technique to fabricate ZnO of very high structural quality, which can eventually be used as an alternative to bulk ZnO substrates.

Layer by layer growth of ZnO on (0001) sapphire substrates by radical-source molecular beam epitaxy

“…These properties of the (0002) diffraction peak indicate extremely good ordering along the growth direction of ZnO (0001) as a consequence of well controlled layer by layer epitaxial growth. Similar to the case of hydrogen peroxide MBE [1][2][3][4] the asymmetric XRD scan was very wide indicating the presence of twist in our layers. In both cases we used MgO buffer layer and we will proceed with the detailed investigations of the spinel layer formation on the interface to the sapphire substrate in order to reduce the presence of twist in our layers.…”

“…RHEED oscillations are most pronounced for Zn rich growth, with O/Zn ratios close to 1. The most flat surface morphology of ZnO has been obtained when the O/Zn flux ratio was from 0.7 to 1, since as it was reported previously for the ZnO epitaxial growth employing hydrogen peroxide as an oxidant the growth under O-rich conditions leads to formation of hexagonal pyramids and at higher O/Zn ratios to a 3D growth with final layers formed by c-oriented columnar structures [2][3][4]. Similar to the case of the usage of the hydrogen peroxide source, in the case of the plasma source it is possible to change back the initially 3D growth to the 2D one by the implementation of Zn-rich growth at O/Zn flux ratios of about 0.5-0.7.…”

“…Controlling the crystalline defects in naturally n-type ZnO is the critical issue to obtain p-type ZnO. Previously [1][2][3][4], we developed a cheap and efficient technique for the epitaxial growth of ZnO on Al 2 O 3 (0001) substrates by MBE with the use of hydrogen peroxide as an oxidant. That approach has its limitations concerning growth rate and controllability and it has its advantages to employ a standard oxygen plasma source as the standard alternative for applications where thick epitaxial layers are necessary.…”

Effects of sputtered buffer layer on the characteristics of ZnO:Al films grown on glass substrates using high-temperature H2O generated by a catalytic reaction

“…[5][6][7][8][9][10][11] The use of ZnO in transparent conductive films and optoelectronic devices is particularly desirable because the development of technologies for producing inexpensive solar cells and new light sources with high emission efficiencies is eagerly anticipated. Many growth techniques, including molecular beam epitaxy (MBE), [12][13][14][15] pulsed laser deposition (PLD), [16][17][18][19][20] laser MBE, 3) magnetron sputtering, [5][6][7][8][9][10][11] and metal-organic chemical vapor deposition (MOCVD), [21][22][23][24][25] have been used to prepare ZnO thin films. MOCVD has many merits for industrial applications, including a high growth rate on largearea substrates and a wide choice of metalorganic and oxygen source gases.…”

ZnMgO‐ZnO quantum wells embedded in ZnO nanopillars: Towards realisation of nano‐LEDs

“…Respective deposition rates were controlled using a quartz thickness monitor prior to and after the growth. Oxygen radicals were introduced with an Addon oxygen RF plasma cell operated at 400 W. After chemical treatment the substrates were thermally cleaned at 750 °C in vacuum and in the case of sapphire at 700 °C in oxygen [2][3][4]. Then, a hightemperature (HT) MgO buffer layer was grown on cleaned c-sapphire at 700 °C under oxygen-rich conditions [2][3][4][5].…”