Molecular beam epitaxy growth and doping of III-nitrides on Si(1 1 1): layer morphology and doping efficiency

Abstract Wurtzite GaN layers grown by plasma-assisted molecular beam epitaxy on Si(1 1 1) reveal strong morphology changes as a function of the III/V ratio. For nominally N-rich conditions, GaN nanocolumns are reproducibly grown with diameters ranging from 600 to 1500 A. These nanocolumns are fully relaxed from lattice and thermal strain, having a very good crystal quality characterized by strong and narrow (2 meV) photoluminescence excitonic lines at 3.472–3.478 eV. The nanocolumns generate from a reduced Ga adatoms diffusion due to the excess nitrogen (Ga-balling). Si-doping yields 2×10 19 and 8×10 19 electrons cm −3 in compact GaN and AlGaN (up to 45%) layers, respectively. In addition, Si-doping decreases the threading dislocation density while enhancing the layer biaxial tensile strain. P-type doping with Be, Mg and C is analyzed and compared. Carbon shows a low solubility according to theoretical predictions. Mg-doping is efficient leading to hole densities in the mid 10 17 cm −3 range. Be is the shallowest acceptor level (90–100 meV), but its efficiency is hampered by the generation of deep Be-related traps, most probably V Ga –Be i complexes, and by self-compensation by Be i . Positron annihilation spectroscopy results; the effect of Mg when codoping with Mg+Be, and the presence of a strong Be-related yellow luminescence back these assumptions.

[1]  R. Beresford,et al.  Exciton and donor - acceptor recombination in undoped GaN on Si(111) , 1997 .

[2]  Masahiko Sano,et al.  CONTINUOUS-WAVE OPERATION OF INGAN/GAN/ALGAN-BASED LASER DIODES GROWN ON GAN SUBSTRATES , 1998 .

[3]  N. Bojarczuk,et al.  Selective area metalorganic molecular-beam epitaxy of GaN and the growth of luminescent microcolumns on Si/SiO2 , 1999 .

[4]  F. Calle,et al.  Experimental evidence for a Be shallow acceptor in GaN grown on Si(111) by molecular beam epitaxy , 1998 .

[5]  R. Beresford,et al.  The effect of the III/V ratio and substrate temperature on the morphology and properties of GaN- and AlN-layers grown by molecular beam epitaxy on Si(1 1 1) , 1998 .

[6]  J. Likonen,et al.  THE INFLUENCE OF MG DOPING ON THE FORMATION OF GA VACANCIES AND NEGATIVE IONS IN GAN BULK CRYSTALS , 1999 .

[7]  C. Walle,et al.  Chemical trends for acceptor impurities in GaN , 1999 .

[8]  N. Giles,et al.  The effect of atomic hydrogen on the growth of gallium nitride by molecular beam epitaxy , 1996 .

[9]  Jörg Neugebauer,et al.  Gallium vacancies and the yellow luminescence in GaN , 1996 .

[10]  C. T. Foxon,et al.  Photoluminescence of MBE grown wurtzite Be-doped GaN , 1998 .

[11]  M. Scheffler,et al.  Adatom diffusion at GaN (0001) and (0001̄) surfaces , 1998, cond-mat/9809006.

[12]  L. Dobrzyński,et al.  Observation Of Native Ga Vacancies In Gan By Positron Annihilation , 1997 .

[13]  Sergio I. Molina,et al.  The effect of Si doping on the defect structure of GaN/AlN/Si(111) , 1999 .

[14]  E. Monroy,et al.  Growth optimization and doping with Si and Be of high quality GaN on Si(111) by molecular beam epitaxy , 1998 .