SELECTIVE ETCHING OF n-TYPE GaAs IN A CrO3-HF-H2O SYSTEM UNDER LASER ILLUMINATION

— A wide range of CrO,/HF mixtures in diluted form and under laser illumination (A = 6328 A) have been found to be useful for defect revealing in n-type {100} GaAs. After removal of 0.2 0.4 microns from the GaAs surface, striations, dislocations, stacking faults and inclusions are revealed, so these etchants can be used to study defects in GaAs epitaxial layers. The characteristic features of the etch figures are similar to those obtained with the DABL method (diluted AB etch under laser ill.) but some properties of the Cr03~HF-H20 system are advantageous: the composition of etchants (within wide limits) is not critical for the defect revealing mode (although the kinetics of etching are composition dependent), no precipitates are formed in solution, high reproducibility of the method, no memory effect. These diluted Sirtllike etchants used with laser (DSL) were calibrated with AB-etch and compared with the DABL method.