Dry etching and implantation characteristics of III-N alloys

The wide-gap nitrides GaN, AIN and InN and their ternary alloys are attracting interest for blue-UV emitters, high temperature electronics and as passivation films for other semiconductors. We review the dry etching chemistries that are found to provide smooth anisotropic pattern transfer in these materials, namely Cl2H2, BCl3 or CH4H2 for AlxGa1−xN alloys and CH4H2 for InxGa1−xN alloys. Microwave enhancement of the discharge is useful for increasing the etch rate at fixed d.c. self-bias. Ar+ ion milling rates for the nitrides are typically a factor of 2 lower than for conventional III-Vs such as GaAs and InP. Implant isolation of InxGa1−xN shows similar characteristics to GaAs, namely a several orders of magnitude increase in resistance after implantation with moderate doses of F+ or O+, followed by a further increase with annealing temperature up to about 500°C as hopping conduction is decreased. Minimal diffusion of most implanted dopants is found up to annealing temperatures of 800°C. Prospects for other process modules, especially wet chemical etching and ohmic contacts, will be discussed.