Aug 16, 2018

Preferential In-Water Oxidation around Defects in Undoped LEC Semi-Insulating GaAs Wafers

Boiling an undoped LEC semi-insulating GaAs wafer in deionized water forms an oxide film on the wafer which gives a visual representation of the defects in the wafer. This preferential oxidation of GaAs was found to be promoted by photons. These findings suggest that the density of photogenerated holes, which play the leading role in oxidation, should be high around defects, because defects, such as dislocations and lineage, can absorb hole traps. The oxide film is thus thick in the vicinity of a defect and thinner away from it. The defect pattern can be extinguished by carrier doping prior to boiling.

Source:IOPscience

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Aug 3, 2018

Thermoelastic Analysis of Slip Defect Generation on GaAs Wafers

In this work we develop the thermoelastic analysis for prediction of slip defect generation on (001) GaAs wafers, by means of the finite element method taking into account the anisotropic structure and slip system of dislocation. The analysis for a completely circular wafer predicts that longer slip defect lines are generated at the wafer edge of θ=π/8+Δ+nπ/2, 3π/8-Δ+nπ/2 (Δ is about 3°) and the prediction well agrees with the result of the wafer heating experiment. This demonstrates that our anisotropic analysis is more accurate than simple isotropic analysis which predicts slip defect generation at the wafer edge of θ=π/8+nπ/4. According to this thermoelastic analysis, we can additionally confirm that longer slip defect lines are more prone to be generated at the <110> orientation flat (OF) edge than at the circular edge. Finally, we suggest the method of preventing slip defect generation.


Source:IOPscience

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