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 voltag
es 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 a
n 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 unetche
d, and the etched sidewall forms an angle of 22 degrees to the surface
normal.