Reactive ion etching of GaN layers using SF6

The characteristics of reactive ion etching of gallium nitride layers, using SF6 etching gas are investigated. The GaN etch rate is examined by varying the bias voltage and the flow rate of SF6. For bias voltages in the range of 250 V to 400 V, the etch rate is found to increase with voltage, attaining a maximum rate of 167 Angstrom min(-1) at 400 V. The rate also increases with increasing SF6 flow. The addition of an inert gas, Ar, or of a reactive gas, CHF3, is found to barely affect the etch rate. Surface morphology after etching is checked by atomic force microscopy and scanning electron microscopy, which show that the smoothness of the etched surface is comparable to that of the unetched, and the etched sidewall forms an angle of 22 degrees to the surface normal.