AVS 50th International Symposium
    Semiconductors Tuesday Sessions
       Session SC-TuA

Invited Paper SC-TuA3
Chemical Complexities of AlGaInN MOCVD

Tuesday, November 4, 2003, 2:40 pm, Room 321/322

Session: Compound Semiconductor Growth and Processing
Presenter: J.R. Creighton, Sandia National Laboratories
Authors: J.R. Creighton, Sandia National Laboratories
G.T. Wang, Sandia National Laboratories
M.E. Coltrin, Sandia National Laboratories
W.G. Breiland, Sandia National Laboratories
Correspondent: Click to Email
We have used a variety of experimental techniques to investigate possible sources of the parasitic chemical reactions that occur during AlGaInN MOCVD. Growth rates for GaN, AlGaN, and InGaN were measured over a wide range of reactor conditions and compared to reactive flow simulations in order to test possible parasitic chemical reaction mechanisms. All of our results indicate that the parasitic chemical reactions require high temperatures and occur in the boundary layer near the growing surface. These reactions ultimately lead to the formation of nanoparticles, which we have recently observed using in situ laser light scattering. Thermophoresis keeps the nanoparticles from reaching the surface, so the material tied-up in nanoparticles cannot participate in the thin film deposition process. In the case of AlN, the particle size was determined to be 48 nm, and the particle density was in the range of 10@super 8-9@ cm@super-3@. At these densities a significant fraction (20% or more) of the input Al is converted into nanoparticles. We have also directly examined precursor chemistry in the 30-300°C range using in situ FTIR. All three commonly used group-III precursors form adducts with ammonia, but this reaction is entirely reversible for trimethylgallium and trimethylindium. In this temperature range only trimethylaluminum reacts irreversibly with ammonia, evolving methane and forming the expected (CH@sub 3@)@sub 2@Al-NH@sub 2@ product. (Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.).