Hi all. Apologies for joining in order to ask a question - very bad form. I promise to answer at least one myself! Anyway... Any good tips for roughening a GaAs surface? I'm working with a GaAs(-based) wafer with (curses!) a polished back face, and am trying to avoid the possibility of multiple optical reflections between the two faces of the wafer. I therefore need my back surface to be rough (in fact, just like any old one-side-polished substrate!). I'd guess that it's going to involve mechanical abrasion followed by a preferential etch, but if anyone can be more specific and save me time (and ideally give me a good chemical-only HF-free method, please Santa), that'd be extremely helpful. I've blackened many a surface in my time, but it's remarkably hard to do it when you actually want to... ;-) Cheers, Andy