Optimization of the surface morphologies and electron mobilities in GaN grown by plasma-assisted molecular beam epitaxy

Heying, B.; Smorchkova, I.; Poblenz, C.; Elsass, C.; Fini, P.; Den Baars, S.; Baars, S. Den; Mishra, U.; Speck, J. S.; Speck, J.S.
October 2000
Applied Physics Letters;10/30/2000, Vol. 77 Issue 18
Academic Journal
The morphology and electrical properties of homoepitaxial GaN layers grown by molecular beam epitaxy at 720 °C were investigated as a function of Ga/N ratio. GaN films grown with low Ga/N ratios (N-stable regime) are semi-insulating and have heavily pitted morphologies. GaN films grown with higher Ga/N ratios (intermediate regime) have fewer pits with areas of atomically flat surface. The room-temperature electron mobilities in samples grown in the intermediate regime are greater than 800 cm2/V s and increase with Ga/N ratio. At the highest Ga/N ratios (Ga-droplet regime), Ga droplets formed on the surface during growth. Although the surface morphology is free of pits and atomically flat for films grown within the Ga-droplet regime, the mobility decreases significantly compared to films grown in the intermediate regime. Room-temperature electron mobilities as high as 1191 cm2/V s were measured in a GaN film grown with the highest Ga/N ratio within the intermediate regime. © 2000 American Institute of Physics.


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