Determination of the Dislocation Network Density in GaAs Using Thermal Wave Microscopy

Abstract

AbstractThe pattern and density of dislocations in GaAs is thought to affect the ultimate performance of finished devices. Previous studies of dislocation networks have usually involved molten KOK etching of GaAs wafers or X-ray topography. A relatively new technique, Thermal Wave Microscopy (TWM), offers an alternative method of analysis. High frequency blanking of the scanning electron beam in an SEM produces thermal waves that propagate approximately 1–2 wavelength through a sample, are then carried by thermoacoustic waves and detected by a piezoelectric transducer. Dislocations, microcracks, and voids will disturb this wave and the resulting image will show a change in contrast (bright or dark) at the defect site. Resolution is dependent on the thermal properties of the material being analyzed as well as on the accelerating voltage, beam current, beam blanking frequency and phase of the electron beam. TWMim ages of dislocation networks in as-received GaAs are very similar in appearance to the results of molten KOH etching. TWM is a relatively new technique for microanalysis. Its full range of applications are still being explored. For determination of dislocation networks it is a faster, less cumbersome method of analysis. TWM is a basically nondestructive technique involving none of the uncertainties of molten KOH etching (etch time, etch uniformity). For this reason TWM is recommended as an alternative analytical technique.