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ZnMgO-ZnO based Heterostructures and Nanopillars grown by MOVPE

Andreas Waag 1Th. Gruber 2C. Kirchner 2R. Kling 2F. Reuss 2H. Wehmann 1Andrey Bakin 1

1. TU Braunschweig, Institute of Semiconductor Technology (IHT), Hans Sommer Str. 66, Braunschweig 38106, Germany
2. Ulm University, Department of Semiconductor Physics, Albert Einstein Allee 45, Ulm 89081, Germany

Abstract

Due to its specific optical and magnetic properties - ZnO seems to be a very versatile material platform in the field of optoelectronics, magnetoelectronics, and nanoelectronics. In particular, a self-organized growth mode can be initiated in order to fabricate ZnO nanopillars with a quite homogenous size distribution. ZnO nanostructures offer an unusual adventage: the surface oxidation obviously does not present a problem. Up to now, the work on the ZnO growth by MOVPE (important industrial standard) is relatively limited. Here, we report on the development of MOVPE technology in order to establish a basis for the exploitation of ZnO hetero- and nanostructures. While conventional precursors are available for the metal components (DEZn, Cp2Mg), the choice of an adequate oxygen precursor for the growth of ZnO and ZnMgO is very important. We have used i-PrOH and t-BuOH for the low temperature growth (300÷500C), and N2O for the high temperature growth (600÷950C). ZnO or sapphire have been used as substrates. The incorporation of Mg turns out to be difficult due to pronounced prereactions of the Mg precursor. With a careful process control, we were able to fabricate ZnMgO layers with Mg content of up to 9%, and to incorporate these as barriers in ZnMgO/ZnO quantum well structures. Now those barriers allow the fabrication of heterostructures, which include cladding and waveguide layers for optically pumped lasing. In addition, MOVPE can be used to initiate a growth mode resulting in the self-organized growth of ZnO nanopillars with a typical width of only 50 nm and a height of up to 5 μm. Despite small diameter, these free-standing nanopillars show intense PL spectra, with FWHM below 0.5 meV. HRXRD analysis shows that these nanopillars - depending on the growth mode - can be almost completely c-oriented. The fabrication of ZnMgO-ZnO based quantum well structures and nanostructures will be described, including an analysis of their structural and optical properties.

 

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Related papers

Presentation: invited oral at E-MRS Fall Meeting 2004, Symposium F, by Andreas Waag
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-14 15:26
Revised:   2009-06-08 12:55