Scaling up a horizontal HVPE reactor C.E.C. Dam a , T. Bohnen a, ⁎ , C.R. Kleijn b , P.R. Hageman a , P.K. Larsen a a Institute for Molecules and Materials, Applied Materials Science, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands b Department of Multi Scale Physics, Delft University of Technology, Prins Bernhardlaan 6, 2628 BW Delft, The Netherlands Available online 12 April 2007 Abstract We have constructed a hydride vapor phase epitaxy (HVPE) reactor capable of producing four inch Gallium Nitride wafers. The design is based on a previously built and successfully operated two inch wafer system [Dam C.E.C., Grzegorczyk A.P., Hageman P.R., Dorsman R., Kleijn C.R., Larsen P.K., The effect of HVPE reactor geometry on GaN growth rate—experiments versus simulations , J. Cryst. Growth 271 (2004) 192; Dam C.E.C., Hageman P.R., Larsen P.K., Carrier gas and position effects on GaN growth in a horizontal HVPE reactor: an experimental and numerical study, J. Cryst. Growth 285 (2005) 31; Dam C.E.C., Grzegorczyk A.P., Hageman P.R., Larsen P.K., Method for HVPE growth of thick crack-free GaN layers, J. Cryst. Growth 290 (2006) 473 [1-3]], essentially by geometrically scaling up all dimensions by a factor λ =2. To obtain identical processes in both reactors, we applied a scaling analysis based on the dimensionless numbers describing the processes in the system, i.e. the Reynolds, Grashof, and surface Damköhler numbers. When scaling up the reactor dimensions by a factor λ, these dimensionless numbers can be kept constant by adjusting the pressure and the inlet velocities of the gasses as p ∝ λ - 3/2 and ν∝λ 1/2 respectively, and the inlet mole fraction of the rate limiting precursor GaCl as f in ∝λ. With the applied scaling rules, identical flow and deposition profiles are obtained in the scaled-up reactor. To verify our scale-up theory, we simulated both systems using computational fluid dynamics (CFD). The calculated flow path lines, concentration and depositions contours of the smaller and larger systems, when correctly scaled, agree very well with each other. © 2007 Elsevier B.V. All rights reserved. Keywords: Computer simulation; Fluid dynamics; Hydride vapor phase epitaxy; Semiconducting gallium nitride 1. Introduction One main problem obstructing the growth of high perfor- mance gallium nitride devices is the absence of native, or at least lattice matched, substrates. Such substrates would allow growth with a lower dislocation density which would be beneficial for the device quality and life time. One option to overcome this problem is to use GaN itself as it would meet most substrate requirements for zero or low thermal expansion and lattice constant mismatch [4]. Hydride vapor phase epitaxy (HVPE) is the best tool to grow thick GaN layers on a foreign substrate at 100 μm/h or more. After removal of the substrate, e.g. by laser lift off or chemical/ mechanical removal, these layers can be used as quasi- substrates for homoepitaxial growth [5–10]. Substrates obtained in this way are slowly becoming commercially available as the thickness of GaN layers grown on two inch or smaller substrates increases. For heteroepitaxy on two inch wafers by HVPE growth crack free GaN layers around 300 μm have been achieved by various groups [3,11,12] while HVPE homoepitaxy can yield 2 mm thick layers [13]. This increase of both thickness and quality of GaN wafers is for a large part due to the careful optimization of the design of the reactors, the gas flows used and the applied growth methods; basically it is the result of an accumulation of knowledge with time and experience. In the future it seems likely that thick high quality two inch wafers will be followed by similar GaN boules, only with diameters of four inches or even larger. Increasing the wafer size would, in most cases, require a redesign of the reactor and in turn a new and possibly lengthy optimization process. One cannot, for growth on four inch substrates, simply double all the growth parameters as some scale with the dimension in a Surface & Coatings Technology 201 (2007) 8878 – 8883 www.elsevier.com/locate/surfcoat ⁎ Corresponding author. Applied Materials Science, Institute for Molecules and Materials, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands. Tel.: +31 24 3653432; fax: +31 24 3652620. E-mail address: T.Bohnen@science.ru.nl (T. Bohnen). 0257-8972/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2007.04.009