Andy, I can't say I have done this before, but you may find Di : H2O2 : H3PO4 (1:4:3) will work for you @ 38 degrees. I do it mechanically as I can't have anything happen to my front side. Brent Andy Irvine wrote: > 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