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 Cl-2-H-2, BCl3 or CH4-H-2 for AlxGa1-xN alloys and CH4-H-2 for InxGa(1-x)N 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 m-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 degrees C as hopping conduction is decreased. Minimal diffusion of most implanted dopants is found up to annealing temperatures of 800 degrees C. Prospects for other process modules, especially wet chemical etching and ohmic contacts, will be discussed.