Hi Scott,

  I can tolerate upto 1mil of undercut. And I think about 5microns per minute is
"fast" enough. Thanks for your reply.

  Deepa

Scott McWilliams  wrote:
  Hi Deepa, it may help us respond if you can give an indication of how much
mask undercut you can tolerate. Many chemicals etch GaAs "fast" and the
degree of anisotropy can depend on the crystal planes. Also, can you define
what is acceptably fast?