Dry Etch Damage in InN, InGaN and InAlN

Abstract

Damage introduction in III-V nitrides during dry etching can be simulated by exposing the samples to pure Ar plasmas for study of the physical (ion-bombardment) effects. Changes in conductivity of InN, In_0.5Ga_0.5N and In_0.5Al_0.5N layers exposed to Ar plasmas under both Electron Cyclotron Resonance and reactive ion etching conditions have been measured as a function of rf power, pressure and exposure time. The combination of high microwave and high rf powers produces large increases (10–10⁴ times) in sheet resistance of the nitrides, but conditions more typical of real etching processes (rf power < 150W) do not change the bulk electrical properties. The nitrides are more resistant to damage introduction than other III-V semiconductors. The removal of damage-related traps occurs with an activation energy of ~2.7eV. High ion currents during ECR etching can produce substantial conductivity changes, whereas the lower currents under RIE conditions do not affect the nitrides. It is difficult to avoid preferential loss of N in the near-surface of these materials, which leads to leakage currents in rectifying metal contacts deposited on these surfaces.