High temperature surface degradation of III-V nitrides

The surface stoichiometry, surface morphology and electrical conductivity of AlN, GaN, InN, InGaN and InAlN was examined at rapid thermal annealing temperatures up to 1150 degrees C. The sheet resistance of the AlN dropped steadily with annealing, but the surface showed signs of roughening only above 1000 degrees C. Auger Electron Spectroscopy (AES) analysis showed little change in the surface stoichiometry even at 1150 degrees C. GaN root mean square (RMS) surface roughness showed an overall improvement with annealing, but the surface became pitted at 1000 degrees C, at which point the sheet resistance also dropped by several orders of magnitude, and AES confirmed a loss of N from the surface. The InN surface had roughened considerably even at 650 degrees C, and scanning electron microscopy (SEM) showed significant degradation. In contrast to the binary nitrides the sheet resistance of InAlN was found to increase by similar to 10(2) from the as grown value after annealing at 800 degrees C and then remain constant up to 1000 degrees C, while that of InGaN increased rapidly above 700 degrees C. The RMS roughness increased above 800 degrees C and 700 degrees C respectively for InAlN and InGaN samples. In droplets began to form on the surface at 900 degrees C for InAlN and at 800 degrees C for InGaN, and then evaporate at 1000 degrees C leaving pits. AES analysis showed a decrease in the N concentration in the top 500 Angstrom of the sample for annealing greater than or equal to 800 degrees C in both materials.