Jul 24, 2018

Etching Characterization of {001} Semi-Insulating GaAs Wafers

The characteristics of {001} semi-insulating GaAs wafers have been investigated by the etching/optical microscopy. New etch features such as groove have been revealed in only LEC crystals together with ridge features by an AB etch, but not in boat-grown crystals. The groove features are specifically revealed on gathering and twisting dislocations such as cell or lineage structures, and coincide with each dislocation lying near the surface. Small pits along the ridge features have been revealed in undoped LEC crystal, but not in undoped boat grown crystals. The distribution of the ridge features with the small pits correlates with that of 0.80 eV photoluminescence intensity in the wafer.


Source:IOPscience

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Jul 1, 2018

Nondestructive and Noncontact Observation of Microdefects in GaAs Wafers with a New Photo-Thermal-Radiation Microscope

A nondestructive and noncontact method for observation of microdefects in GaAs wafers has been developed with a new photo-thermal-radiation (PTR) microscope. We measured the PTR signal as a function of excitation energy (PTR spectrum) and the spatial distribution of PTR intensity (PTR image) of n-GaAs wafers at room temperature. We found that the PTR spectra have a peak due to a nonradiative state of microdefects at wavelengths ranging from 895 to 903 nm. The present PTR image shows inhomogeneities of microdefect density in GaAs wafers which cannot be observed by X-ray topography.


Source:IOPscience

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