Solid-Phase Epitaxial Growth of Amorphized GaAs: The Influence of Microscopic and Macroscopic Non-Stoichiometry
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ABSTRACT The solid-phase epitaxial growth of amorphized GaAs has been characterized to investigate the influence of both microscopic and macroscopic non-stoichiometry on the onset of twinning and subsequent interfacial non-planarity. Microscopic non-stoichiometry or equivalently, chemical disorder on an atomic scale, was produced by implanting samples with equal doses of both Ga and As ions. In such samples, the onset of twinning and interfacial nonplanarity where independent of the energy deposited in vacancy production, the latter considered a first estimate of relative differences in microscopic non-stoichiometry between samples. Twinning and interfacial non-planarity are thus independent of microscopic non-stoichiometry or alternatively, microscopic non-stoichiometry may approach saturation over the given dose range. In contrast, macroscopic non-stoichiometry produced by implanting samples with Ga or As ions influenced both the onset of twinning and interfacial non-planarity. Excess Ga was observed to have a greater effect than excess As. The influence of a macroscopic non-stoichiometry may be indicative that the availabiltiy of a lattice constitutent and/or defect is rate-limiting during solidphase epitaxial growth. Macroscopic non-stoichiometry may also yield preferrential nuclueation sites for twinning and in the presence of excess Ga, molten precipitates could contribute to an observed rapid amorphous-to-crystalline transformation. INTRODUCTION The solid phase epitaxial growth (SPEG) of amorphized GaAs at temperatures of -200400 0 C yields an undesireable microstructure in the form of twins and stacking faults. Factors potentially responsible for this defective recrystallization include a critical, locally-deposited energy density [1,2], plastic deformation [3], non-planarity or defect precipitation at the amorphous/crystalline (a/c) interface [4-6] and/or non-stoichiometry [1,7,8]. The latter, yet to be examined in detail, can be of a macroscopic or microscopic nature - macroscopic nonstoichiometry results from the implantation of a lattice constituent while microscopic nonstoichiometry or equivalently, chemical disorder at the atomic level, results from the statistical nature of the ion stopping and recoiling processes. For the present study, the influence of nonstoichiometry on the onset of twinning and interfacial non-planarity during the SPEG of amorphized GaAs was investigated by implanting samples with Ga or As ions (macroscopic) or Ga and As ions (microscopic). With such an implantation regime, impurity effects are negated and for the first time the relative influence of the two forms of non-stoichiometry can be
differentiated.
393 Mat. Res. Soc. Symp. Proc. Vol. 398 0 1996 Materials Research Society
EXPERIMENTAL
SSemi-insulating GaAs wafers of (100) orientation were implanted with Ga and/or As ions over the dose range 1e14-1e16 /cm2 where the ion energies were selected to yield a common projected range for the two species. Samples were subsequently annealed in air at a temperature of 260 0 C w
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