Abstract
Plasma-assisted molecular beam epitaxy (PA-MBE) is now widely used for the growth of group III-nitrides. Many years ago it became clear that during PA-MBE there is unintentional doping of GaN with boron (B) due to decomposition of the pyrolytic boron nitride (PBN) cavity of the RF plasma source. In this paper we discuss the unintentional B incorporation for PA-MBE growth of GaN and AlxGa1−xN using a highly efficient RF plasma source. We have studied a wide range of MBE growth conditions for GaN and AlxGa1−xN with growth rates from 0.2 to 3µm/h, RF powers from 200 to 500W, different nitrogen flow rates from 1 to 25 sccm and growth times up to several days. The chemical concentrations of B and matrix elements of Al, Ga, N were studied as a functions of depth using secondary ion mass spectrometry (SIMS). We demonstrate that boron incorporation with this highly efficient RF plasma source is approximately 1×1018 to 3×1018cm−3 for the AlxGa1−xN growth rates of 2 – 3µm/h.
Highlights
IntroductionPlasma-assisted molecular beam epitaxy (PA-MBE) is widely used for the growth of group III-nitride layers and device structures
Plasma-assisted molecular beam epitaxy (PA-MBE) is widely used for the growth of group III-nitride layers and device structures.Many years ago it became clear that in PA-MBE using a nitrogen RF plasma source there is unintentional doping of the layers with boron (B) due to decomposition of pyrolytic boron nitride (PBN) cavity and the PBN aperture plate of the RF plasma source [1]
In this study we have investigated the influence of the PA-MBE conditions on unintentional boron (B) incorporation in GaN and AlxGa1−xN layers grown with the wide range of RF plasma sources
Summary
Plasma-assisted molecular beam epitaxy (PA-MBE) is widely used for the growth of group III-nitride layers and device structures. We have recently used the PA-MBE technique for bulk crystal growth and have produced free-standing layers of zinc-blende and wurtzite GaN and AlxGa1−xN up to 100 μm in thickness [3,4]. Majority of the manufacturers are exploring the route of increasing the conductance of the aperture plates of the RF plasma cavity in order to achieve significantly higher total flows of nitrogen through the plasma source. First tests of the latest model of Riber RF nitrogen plasma source with 5880 holes in the aperture plate, produced even higher growth rates for thin GaN layers up to 7.6 μm/h, but with nitrogen flow rates of about 25 sccm [6]. In this study we have investigated the influence of the PA-MBE conditions on unintentional boron (B) incorporation in GaN and AlxGa1−xN layers grown with the wide range of RF plasma sources
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