THE BANDGAP-SELECTIVE PHOTOELECTROCHEMICAL ETCHING OF GAAS/ALXGA1-XAS HETEROSTRUCTURES WITH VARYING MOLE FRACTION

We have demonstrated the highly selective removal of low aluminum (Al) mole-fraction AlxGa1-xAs layers from those with higher Al mole-fraction using the wet photoelectrochemical (PEC) etch process. AGaAs/AlxGa1-xAs semiconductor structure with layers of varying Al mole-fraction was examined. The sample was etched in a (1:20) HCl:H2O electrolyte solution. A Ti/sapphire laser was used as the light source to tune the incident photon energy between the various bandgaps of the heterostructure layers. Relative etch rates >10(4):1 and >10(3):1 were found for mole fraction differences in x of 0.15 and 0.05, respectively. The selectivity was examined as a function of incident wavelength.