Reduction of Threading Dislocation Density in InN Film Grown with in situ Surface Modification by Radio-frequency Plasma
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.218
Reduction of Threading Dislocation Density in InN Film Grown with in situ Surface Modification by Radio-frequency Plasma-excited Molecular Beam Epitaxy F. B. Abas1, R. Fujita1, S. Mouri1, T. Araki1, and Y. Nanishi1 1 Department of Electrical and Electronic Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga, 525-8577 Japan.
ABSTRACT
The objective of this study was to investigate the relationship between the thickness of N radical irradiated InN template with crystallographic quality and electrical properties of InN film grown with the previously proposed method, in situ surface modification by radical beam irradiation. In this study, three InN samples were grown with this method on different thickness of irradiated templates. The crystallographic quality of InN films was analyzed by X-ray diffraction and the electrical properties were studied by Hall effect measurement. InN grown on 100 nm thick irradiated template shows lower full-width at half-maximum of X-ray rocking curves and lower carrier concentration compared to InN grown on 200 nm and 450 nm thick irradiated templates. Transmission electron microscopy revealed that threading dislocation density in the InN film decreased by an order of magnitude to ~4.6u109cm-2. These results suggest that this method is possible for reduction of threading dislocation density in InN and the thickness of irradiated template should be minimized for higher crystallographic quality and electrical properties of the entire InN film.
INTRODUCTION Recently, nitride-based semiconductors have attracted much attention owing to their unique properties [1, 2]. Their bandgap energy span from ~6.2 eV (AlN) to ~3.4 eV (GaN) and ~0.65 eV (InN). They are very attractive for various optoelectronic devices applications such as super high-efficiency solar cells [3], light-emitting diodes [4] and laser diodes [5]. Furthermore, InN which has the highest electron mobility among them is a very promising material for future high-speed electronic device applications [6]. However, high crystalline quality InN is the most difficult to be obtained due to its low dissociation temperature [7] and the lack of lattice-matched substrates. These factors result in a high density of threading dislocations in the InN epitaxial layers. To date, several techniques have been proposed for reduction of threading dislocation density in InN [8-11] but most of these methods require ex-situ preparations and are only effective for a very small area of InN crystal. Therefore, a new approach which provides simple
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growth process but effective for dislocation reduction in a large area of InN crystal is necessary. Previously, we have investigated the applicability of in situ surface modification by radical
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