The optical and transport properties of wurtzite GaN layers which had been grown, via plasma-assisted molecular-beam epitaxy, onto Si(111) substrates, were investigated. An emission at 3.455eV, after continuous-wave and time-resolved luminescence analyses of undoped and Si-doped GaN layers, was attributed to excitons that were bound to Si donors with an optical binding energy of 0.050eV. A common origin for this peak, in both undoped and Si-doped GaN, was supported by secondary-ion mass spectroscopic data that revealed Si diffusion from the substrate and into the GaN layer at growth temperatures above 660C. At the same time, Ga diffusion into the Si substrate generated a highly p-type conductive layer at the GaN/Si interface, and led to unreliable Hall results for undoped and lightly-doped layers. Positron annihilation data revealed concomitant vacancy cluster generation at the GaN/Si interface in samples which had been grown at temperatures above 660C. No trace of the so-called yellow band was detected in either undoped or Si-doped samples.

Effect of Ga/Si interdiffusion upon optical and transport properties of GaN layers grown on Si(111) by molecular-beam epitaxy E.Calleja, M.A.Sánchez-García, D.Basak, F.J.Sánchez, F.Calle, P.Youinou, E.Muñoz, J.J.Serrano, J.M.Blanco, C.Villar, T.Laine, J.Oila, K.Saarinen, P.Hautojärvi, C.H.Molloy, D.J.Somerford, I.Harrison: Physical Review B, 1998, 58[3], 1550-9