DOPANT SELECTIVE PHOTOELECTROCHEMICAL ETCHING OF GAAS HOMOSTRUCTURES

We have examined the etch selectivity of homostructures of 1-mu-m of n+GaAs (2 x 10(18) cm-3) on both a nonintentionally doped (NID) substrate and a p+GaAs (2 x 10(18) cm-3) substrate. Samples were etched at 1.38 W/cm2 in a 1:20 HCl:H2O electrolyte over a bias range from -0.5 to +0.5 V. The selectivity of the n+GaAs/p+GaAs structure is extremely high at greater-than-or-equal-to (15,000:1). The selectivity of the n+GaAs/NID GaAs structure is significantly less, on the order of (30:1). The relative etch selectivity of the latter structure has a strong dependence on applied bias.