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Thermal decomposition mechanisms of tetraethylgermane in metal-organic chemical vapor deposition

1998; Elsevier BV; Volume: 44; Issue: 2 Linguagem: Inglês

10.1016/s0165-2370(97)00077-6

1873-250X

Jamal El Boucham, F. Maury, R. Morancho,

Semiconductor Lasers and Optical Devices

Polycrystalline Ge thin films have been grown by MOCVD in an atmospheric laminar flow reactor using GeEt4 as precursor. Hydrogen is required to remove the carbon contamination of the films which is observed under inert atmosphere. The decomposition mechanism of GeEt4 in the CVD reactor has been investigated from analyses of the gaseous by-products in a variety of chemical environments. The overall reaction is the growth of Ge thin film with formation of H2 and C2H4 as gaseous by-products, likely by the β-hydrogen elimination mechanism rather than radical pathways. The decomposition process under inert atmosphere is predominantly homogeneous with likely formation of intermediates as nutrient species for the film. Secondary heterogeneous processes including polymerization reactions or incomplete removal of the ligands and subsequent dehydrogenation lead to carbon contamination of the layers. In ambient H2, the formation of C2H6, likely by the hydrogenation of C2H4, prevents the polymerization of the olefin and accounts for the beneficial influence of H2 in this low temperature deposition process of pure Ge thin films.