38 is immersed in the etchant solution 26 the positive plate 32 of the battery 34 is also connected to a second electrode 40 the connections between the plate 28 electrode 38 and second electrode 40 allow a bias to be applied to the masking layer 16 the amount of the bias being the voltage produced by the battery 34 laser energy 42 is then shined through the container 44 onto the top mask surface 22 of the substrate 10 the laser energy 42 must be above the bandgap energy of the group iii nitride layer 14 or the group iii nitride layer will not be etched the laser energy 42 assists the etchant solution 26 in etching a well 46 in the group iii nitride layer 14 exposed to the openings 24 by providing energy to the openings 24 illuminated by the laser energy 42 examples of etching rates achieved using the method of the invention are described below for comparison etching rates achieved using other techniques are also described 1 etching rates using masking layer 16 no laser energy 42 and etchant solution 26 of 1 10 hcl h 2 o without using the laser energy 42 a substrate 10 with a group iii nitride layer 14 and a masking layer 16 was immersed in a 1 10 hcl h 2 o etchant solution 26 after 37 5 hours no significant etching was observed in the group iii nitride layer 14 2 etching rates using laser energy 42 etchant solution 26 of 1 10 hcl h 2 o but no masking layer 16 without a masking layer 16 and again using a 1 10 hcl h 2 o etchant solution 26 adding laser energy 42 with an energy output.