The Bandgap‐Selective Photoelectrochemical Etching of GaAs / Al x Ga1 − x As Heterostructures with Varying Mole Fraction

The authors have demonstrated the highly selective removal of low aluminum (Al) mole-fraction Al[sub x]Ga[sub 1[minus]x]As layers from those with higher Al mole-fraction using the wet photoelectrochemical (PEC) etch process. AGaAs/Al[sub x]Ga[sub 1[minus]x]As semiconductor structure with layers of varying Al mole-fraction was examined. The sample was etched in a (1:20) HCl:H[sub 2]O 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[sup 4]:1 and >10[sup 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.