SOLID-PHASE EPITAXIAL-GROWTH OF AMORPHISED GAAS IN THE PRESENCE OF IMPLANTATION-INDUCED MICROSCOPIC NONSTOICHIOMETRY

Compound semiconductors typically recrystallise in a defective, twinne d manner during low-temperature annealing. A variety of factors includ ing non-stoichiometry potentially contribute to the onset of this twin ning. For the present report, the influence of non-stoichiometry on th e solid-phase epitaxial growth (SPEG) of GaAs has been examined. Two f orms of microscopic non-stoichiometry present after the co-implantatio n of both Ga and As ions were considered: that due to the unequal reco il of the lattice constitutents resulting from differences in mass and that due to the statistical nature of the ion stopping and recoiling processes. (The latter is the chemical disorder on a microscopic scale subsequent to a quenched collision cascade.) Multiple in-situ and ex- situ characterisation techniques have been utilised including transmis sion electron microscopy, Rutherford backscattering spectrometry, time -resolved reflectivity and double-crystal X-ray diffraction. From such measurements, it was apparent that non-stoichiometry due to the unequ al recoil of the lattice constituents was not responsible for the defe ctive SPEG of amorphised GaAs. Furthermore, the onset of twinning and subsequent interfacial non-planarity were independent of the energy de posited in vacancy production, the latter considered a first estimate of relative differences in chemical disorder. This was potentially ind icative of the saturation of this form of non-stoichiometry at or belo w the dose required for amorphisation.