LASER-ENHANCED MATERIAL SELECTIVITY IN N-GAAS N-AL0.4GA0.6AS HETEROSTRUCTURES/

We demonstrate the effectiveness of controlled surface illumination to enhance the material selectivity at n-GaAs/n-Al0.4Ga0.6As heterojunct ions. Selectivities were measured using 785 and 711 nm light in a 5 we ight percent aqueous nitric acid etchant at room temperature. The high est selectivity observed was an improvement over the unilluminated cas e by a factor of 1700. Potential barriers associated with the n-GaAs/n -Al0.4Ga0.6As junction reduced the selectivity of the etch by 50%. A m odel based on the dissolution of substrate material is presented that relates the selectivity of the etch to the wavelength and intensity of the illuminating light for wavelengths between the cutoff wavelengths of GaAs and Al0.4Ga0.6As. No significant effect on the etch rate was noted for the n-Al0.4Ga0.6As material at wavelengths of 711 and 785 nm .