AlGaAs is usually accomplished with a BCl3/Cl2 chemistry using a non-selective processes at a very low pressure. Processes have been developed to etch GaAs/AlGaAs sandwich structures at rates over 2500 Å /min
20 micron GaAs/AlGaAs mesa with photoresist removed. The bottom 10 microns is GaAs only. Argon, Cl2, RIE/ICP turbo pump, 1700 Å/min, Selectivity (GaAs:PR = 2.1:1), 4:1 selectivity to PR, +/- 4% uniformity.
This Chlorine based process will etch at rates over 5000 Å /min, whist still producing smooth sidewalls with no undercut.
GaN structures are found in a variety of photonic devices including photo detector, lasers, and LED’s. Typically these structures are patterned with a thick coat of photoresist, or a thin metal mask, and the etched surface and sidewalls should be extremely smooth. Processes have been developed with etch rates of over 3,500 Å /min.
Indium Gallium Arsenide Phosphide with SiO2 hard mask. Conditions include a Cl2/BCl3 chemistry with a temp of 100°C. (Courtesy of Applied Opto.)
Etching of InP is usually accomplished with Chorine based chemistries, or Methane/Hydrogen. Rates can be at over 2000 Å /min for chlorine based chemistries. The CH4/H2 process is slow, but it has a very high selectivity to silicon nitride, silicon oxide and photoresist.
Cl2/BCl3, HBr/BCl3 or H2/CH4 chemistries can be used to create a lens in InP with a process developed to produce a 1:1 selectively to PR.