AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM2-ThA

Paper EM2-ThA8
Time of Flight Mass Spectroscopy of Recoiled Ions Comparative Studies of Gallium Nitride Thin Film Deposition By Various Molecular Beam Epitaxial Methods

Thursday, November 5, 1998, 4:20 pm, Room 316

Session: Non-destructive Testing and In-situ Diagnostics
Presenter: A. Bensaoula, University of Houston
Authors: E. Kim, University of Houston
I.E. Berishev, University of Houston
A. Bensaoula, University of Houston
K.L. Waters, Ionwerks
J.A. Schultz, Ionwerks
Correspondent: Click to Email
GaN thin films were successfully grown by electron cyclotron resonance molecular beam epitaxy (ECR-MBE), gas source MBE (GSMBE), and chemical beam epitaxy (CBE). Time of flight mass spectroscopy of recoiled ions (TOF-MSRI) and RHEED were used in-situ to determine the surface composition, the crystalline structure, and the growth mode of GaN thin films deposited by the three MBE methods. The substrate nitridation and the buffer layers were characterized by TOF-MSRI and RHEED. In GSMBE, the Ga/N ratio is found to correlate well with ex-situ optical properties. In the case of CBE, the carbon incorporation determines the surface morphology, the crystalline quality and the optical activity of the epilayers. In the case of CBE, no nucleation was possible until a combination of ECR nitrogen and TEG was used for the low temperature buffer. The carbon and oxygen levels were found to depend greatly on the TeGA flow and substrate temperature. A model describing the main experimental observations will be presented. The model explains both the chemical dissociation of ammonia at low temperatures and the Ga to N TOF-MSRI peak ratio for various Ga and ammonia fluxes.Our study shows that under optimized conditions crystalline epilayers with good optical and surface morphologies can be obtained with all three methods. This work was supported by funds from a NASA cooperative agreement #NCC8-127 to SVEC, a Texas Advanced Research Program Grant # 1-1-27764, and a Texas Advanced Technology Program Grant # 1-1-32061.