High Temperature Surface Degradation of III-V Nitrides

The surface stoichiometry, surface morphology and electrical conductivity of AIN, GaN, InN, InGaN and InAIN was examined at rapid thermal annealing temperatures up to 1150 °C. The sheet resistance of the AIN dropped steadily with annealing, but the surface showed signs of roughening only above 1000 °C. Auger Electron Spectroscopy (AES) analysis showed little change in the surface stoichiometry even at 1150 °C. GaN root mean square (RMS) surface roughness showed an overall improvement with annealing, but the surface became pitted at 1000 °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 °C, and scanning electron microscopy (SEM) showed significant degradation. In contrast to the binary nitrides the sheet resistance of InAIN was found to increase by ˜ 102 from the as grown value after annealing at 800 °C and then remain constant up to 1000 °C, while that of InGaN increased rapidly above 700 °C. The RMS roughness increased above 800 °C and 700 °C respectively for InAIN and InGaN samples. In droplets began to form on the surface at 900 °C for InAIN and at 800 °C for InGaN, and then evaporate at 1000 °C leaving pits. AES analysis showed a decrease in the N concentration in the top 500 Å of the sample for annealing ≥800 °C in both materials.