Dry etching of thin-film InN, AlN and GaN

Smooth, anisotropic dry etching of InN, AlN and GaN layers is demonstrated using low-pressure (1-30 mTorr) CH₄/H₂/Ar or Cl₂/H₂ ECR discharges with additional DC biasing of the sample. The etch rates are in the range 100-400 AA min^-1 at 1 mTorr and -150 V DC for Cl₂/H₂, while higher biases are needed to initiate etching in CH₄/H₂/H discharges. The presence of hydrogen in the gas chemistries is necessary to facilitate equi-rate removal of the group III and nitrogen etch products, leading to smooth surface morphologies.