CHEMICAL BEAM EPITAXY AND CHARACTERIZATION OF GAAS FROM BIS(TERT-BUTYLARSENIDO)DIMETHYLGALLANE DIMER AND BIS(TERT-BUTYLARSENIDO)DIETHYLGALLANE DIMER

The effects of reactor pressure and film growth temperature on growth rates and film properties were investigated for chemical beam epitaxy of GaAs from the single-source precursors bis(tert-butylarsenido)dimet hylgallane dimer, [Me2Ga(mu-As-t-Bu2)]2, and bis(tert-butylarsenido)di ethylgallane dimer, [Et2Ga(mu-As-t-Bu2)]2. Single-crystal epitaxial fi lms could only be obtained at low reactor pressures (5 X 10(-6) Torr). Epitaxial layers, which were highly doped with carbon acceptors (10(1 8)-10(19) cm-3), were deposited from [Me2Ga(mu-As-t-Bu2)]2 at temperat ures of 475-550-degrees-C. Polycrystalline films were obtained at lowe r temperatures, and film growth was not possible below 423-degrees-C. Epitaxial films were obtained from [Et2Ga(mu-As-t-Bu2)]2 over the temp erature range 400-525-degrees-C. The films deposited from [Et2Ga(mu-As -t-Bu2)]2 were inhomogeneous and also contained high levels of carbon (5 X 10(18)-3 X 10(19) cm-3). Growth rates and film properties were fo und to be directly related to reactions of the Ga-Me ligands for [Me2G a(mu-As-t-Bu2)]2 and the Ga-Et ligands for [Et2Ga(mu-As-t-Bu2)]2. A mo del is suggested to explain the results in which a self-limiting mecha nism exists for the deposition of Ga atoms from [Me2Ga(mu-As-t-Bu2)]2 but not from [Et2Ga(mu-As-t-Bu2)]2.