Low-temperature grown compositionally graded InGaN films

A new thin film growth technique known as energetic neutral atomic-beam lithography/epitaxy (ENABLE) provides a large energetic N atom flux and eliminates the need for high substrate temperatures as compared to molecular beam epitaxy, making isothermal growth over the entire InGaN alloy composition range possible without phase separation. 500-800 nm thick compositionally graded InGaN films were grown by ENABLE at ∝450 C with the following structure types: (1) with the Ga-rich material on the surface and (2) with the In-rich material on the surface. Rutherford backscattering spectrometry, transmission electron microscopy, X-ray diffraction, absorption spectroscopy, photoluminescence, and Hall effect measurements were used to assess the thickness, composition, crystalline quality, and optical and electrical properties of the films. The results establish the new ENABLE method as uniquely capable of growing compositionally graded InGaN films and, in the future, InN/GaN heterostructures. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)