Radiation resistance of GaAs-AlGaAs hetero structures doped with isovalentand rare-earth elements

When GaAs-Si and GaAs-AlGaAs heterostructures are exposed to gamma -quanta, radiation stimulated ordering is observed. However, the gettering efficien cy in such systems falls for layer widths more than 1 mum. For this reason we seek effective methods of radiation resistance improvement of materials in which one would expect point radiation defects to be gettered not only a t defect boundaries, but also in the active layer volume. S.i.GaAs-s.i.AlxG a1-xAs-nGaAs:Te heterostructures are presented with epitaxial layers (doped with Yb or undoped), obtained by means of LPE (liquid-phase epitaxy). The electron concentration in nGaAs was found to be (1-3) x 10(18) cm(-3) for w idths 1-3 mum. The samples were exposed to (CO)-C-60 gamma -quanta with dos es of 10(5)-10(7) rad. Investigations of irradiated samples by means of low-temperature (4.2 K) ph oto luminescence have shown considerable decrease of exciton halfwidth in t he boundary spectra of nGaAs:Te:Yb epitaxial layers in comparison with nGaA s: Te layer spectra. This is caused by background impurity gettering which happens on the s.i.AlxGa1-xAs-nGaAs heteroboundaries as well as in deformed regions in the epitaxial layer volume. Formation of such regions is caused by the difference between the covalent radii of Yb atoms and GaAs lattice atoms. The maximum effect of radiation stimulated gettering of dopants in n GaAs epitaxial layers is observed for Yb concentrations which are equal to 10(-4) - 10(-5) atomic fractions in a solution-melt. It is determined that the deformed regions in epitaxial layer volumes and h eteroboundaries could be efficient drains for point radiation defects which form under radiation exposure. The investigations carried out showed that the doping of an epitaxial layers by rare-earth impurities provides conside rable improvement in forming radiation resistant III-V materials. (C) 2001 Elsevier Science Ltd. All rights reserved.