Defects in Superlattices

Abstract
A periodic 20-20 Å GaAs-GaAlAs (30% Al), n-type Si (3 1016 cm-3) doped, 1.7 μm thick, structure has been irradiated with 1 MeV, 3 1015 cm-2 electrons. A series of electron traps situated at energies 0.140, 0.185, 0.34 and 0.55 eV have been detected using Deep Level Transient Spectroscopy. We show that the energy levels and relative concentrations of these traps can be deduced from the energy levels and concentrations of the deep traps known to be created by electron irradiation in n-type GaAs and GaAlAs. These traps emit electrons in a new conduction band, common to both materials, the superlattice miniband situated at 0.140 eV above the conduction band edge of GaAs. This study thus demonstrates that DLTS can be used to characterize deep traps in superlattices.