Deep ultraviolet enhanced wet chemical etching of gallium nitride

We report a study of the ultraviolet (UV) irradiation effects on the wet chemical etching of unintentionally doped $n$ -type gallium nitride (GaN) layers grown on sapphire substrates. When illuminated with a 253.7 nm mercury line source, etching of GaN is found to take place in aqueous phosphorus acid $({\mathrm{H}}_{\mathrm{3}}{\mathrm{PO}}_{\mathrm{4}})$ and potassium hydroxide (KOH) solutions of $p\mathrm{H}$ values ranging from $\text{−1}$ to 2 and 11 to 15, respectively. Formation of gallium oxide is observed on GaN when illuminated in dilute ${\mathrm{H}}_{\mathrm{3}}{\mathrm{PO}}_{\mathrm{4}}$ and KOH solutions. These results are attributed to a two-step reaction process upon which the UV irradiation is shown to enhance the oxidative dissolution of GaN.