화학공학소재연구정보센터
Journal of Crystal Growth, Vol.298, 320-324, 2007
BGaN micro-islands as novel buffers for growth of high-quality GaN on sapphire
We discuss the growth mechanism of GaN films and report very high two-dimensional electron gas (2DEG) mobility in AlGaN/AlN/GaN heterostructures fabricated on sapphire using BGaN micro-islands as novel buffers by metalorganic vapor phase epitaxy. The three-dimensional growth of BGaN (formation of BGaN micro-islands) occurs due to the phase separation of BGaN. However, the surface of the overgrown GaN on the BGaN micro-islands becomes smooth and continuous through the epitaxial lateral overgrowth process. The threading dislocations (TDs) in GaN consist mainly of pure edge-type ones and are effectively annihilated using single and double layers of BGaN micro-islands from 2 x 10(10) to 2 x 10(9) and 2 x 10(8) cm(-2), respectively. An n-type GaN film shallowly doped with Si exhibits an electron concentration and high Hall mobility of 3.0 x 10(16) cm(-3) and 669 cm(2)/Vs at room temperature (RT). Very high Hall 2DEG mobility in an Al0.10Ga0.90N/AlN/GaN heterostructure is obtained: 1910 and 20,600 cm(2)/Vs at RT and 77 K, respectively. The sheet carrier density had almost constant values of 6.9-5.7 x 10(12) cm(-2) in the temperature range from 77 to 500K, indicating that the parallel conduction due to the residual electrons in the GaN underlying layer was negligible. (c) 2006 Elsevier B.V. All rights reserved.