High temperature CVD systems to grow GaN or SiC based structures

Abstract

Silicon Carbide is presently gaining much attention as a material for high temperature, high speed and high power devices. However, fabricating epitaxial SiC or GaN films is still a challenge since very high growth temperatures (up to 1600°C) must be used. This requires a carefully adapted design of reactors to ensure laminar flow conditions and a controlled depletion of the reactants inside the reactor. A second class of materials that is also playing a more and more important role today are the III nitrides (AlN, GaN, InN and alloys consisting of these). These materials are also grown at high deposition temperatures (up to 1300°C). Furthermore, these materials are grown on special buffer layers grown at much lower temperatures and are typically part of complex heterostructures which require abrupt changes of the growth temperature to realize sophisticated optoelectronic and electronic devices. As an example our high quality InGaN layers were grown at about 700°C and the AlGaN cladding layer of a laser or a LED require temperatures higher than 1100°C. In general, both nitrides and SiC are similar in their challenges to the growth equipment. This study uses a family of high temperature reactors to grow SiC and Nitrides. We describe the use of high temperature reactors to grow SiC and Nitrides. The load capacity ranges from single wafer machines to multiple wafer mass production reactors. All these reactors have a two flow injection system allowing a separated inlet of the various reactants. To achieve maximum uniformity of the growth, the Gas Foil Rotation ® Principle is applied. The multiwafer reactors are Planetary Reactors with double rotation of substrates. Extensive modeling has been used in order to find the optimum reactor geometries. Gas flow dynamics, temperature management and the physical and chemical properties of the precursors were considered in these models. Thus an optimization of uniformity and efficiency and a minimization of undesired parasitic reactions has been obtained. This contribution will work out the differences and the similarities of the high temperature growth of both material systems in AIXTRON reactors already established in production. Results on the growth of SiC and GaN will be presented.