I'm looking for reliable (anisotropic) wet etch techniques that give high (~ 10^2) and low aspect ratios for GaAs on Al(0.3)Ga(0.7)As. I have a few in hand, but would be glad for any additional inputs, especially from someone with personal experience, or at least word-of-mouth knowledge. I'm aware of the citric acid/peroxide (which we use) and the ammonia/proxide wet etches. I'm checking to make sure there's not some other wet etch that has been found to be far superior. Any opinions on HCl/H2O2 or others ?