DEEP ELECTRON TRAPS IN GAAS-LAYERS GROWN ON (100)SI SUBSTRATES BY METALORGANIC CHEMICAL VAPOR-DEPOSITION

Deep electron traps in GaAs layers grown on (100) 3 °-off Si substrates by metalorganic chemical vapor deposition were investigated by deep-level transient spectroscopy and a computer simulation method. The four electron traps with the activation energies of 0.81, 0.68, 0.57, and 0.53 eV below the conduction band were measured in GaAs epilayers on Si substrates, whereas only the EL2 level (Ec-0.81 eV) was detected in GaAs on a GaAs substrate. From the dependencies of concentration on the thickness of GaAs epilayer and Si substrate, it was assumed that the Ec-0.57 eV trap might be a Si-dislocation complex defect. The Ec-0.68 eV trap showed a similar behavior to that of the deep trap created in the plastically deformed bulk GaAs, and then its origin was supposed to be a defect induced by a stress due to the differences of thermal expansion coefficient and lattice parameter between Si and GaAs.