Wet etching is a fine tuned art of removing layers of materials from substrates or devices when milling using Focused Ion Beam (FIB) is not an option.
When FIB is used to make trenches on a laser device, some of the Gallium (Ga) ions are deposited on the face of trenches as the depth of milling is increased. This can compromise the characteristics of the device such that you may turn a diode into a resistor.
To remove the deposition of unwanted debris from the side walls of your trenches wet etch can be very useful. Timing in wet etching is everything otherwise you might end up losing the whole device.
Pictures taken using Scanning Electron Microscopy (SEM) are showing the effect of wet etch before and after the process. Cleaner surfaces can be seen after wet etching.
