THE BANDGAP-SELECTIVE PHOTOELECTROCHEMICAL ETCHING OF GAAS ALXGA1-XASHETEROSTRUCTURES 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-fracti on using the wet photoelectrochemical (PEC) etch process. AGaAs/AlxGa1 -xAs semiconductor structure with layers of varying Al mole-fraction w as examined. The sample was etched in a (1:20) HCl:H2O electrolyte sol ution. A Ti/sapphire laser was used as the light source to tune the in cident photon energy between the various bandgaps of the heterostructu re layers. Relative etch rates >10(4):1 and >10(3):1 were found for mo le fraction differences in x of 0.15 and 0.05, respectively. The selec tivity was examined as a function of incident wavelength.