Mechanism of Si outdiffusion in plasma-assisted molecular beam epitaxy of GaN on Si

The mechanism of Si outdiffusion related to the formation of Si‐rich GaN clusters during the growth of GaN‐on‐Si by plasma‐assisted molecular beam epitaxy (PAMBE) has been identified. GaN thin films were grown, on high resistivity Si (111) substrates at Ga‐rich conditions to favour the 2D step‐flow growth mode. Hall‐effect measurements revealed very high electron background concentrations, ranging from 2 x 1018 cm‐3 to 3 x 1019 cm‐3, with degraded carrier mobility in the range of 5‐30 cm2/Vs. SEM examination of surfaces and cross‐sections of the samples revealed the presence of hollow GaN clusters on the film surface and voids at the Si/III‐nitride interface. EDX spot analysis revealed dissolution of Si material in the GaN clusters. Growth of GaN on Si under stoichiometric conditions resulted in films without GaN clusters, which exhibited a serious reduction in carrier concentration, down to 1.4 x 1016 cm‐3, with a simultaneous increase of the carrier mobility to 137 cm2/Vs. C‐V carrier profile measurements were consistent with Hall‐effect measurements and revealed a uniform electron concentration in the GaN film, down to the AlN nucleation layer (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)