MICROSCOPY Vol.45▶No.1 2010
â– Feature Articles: Research Articles by Selected Young Microscopists from East Asia

TEM Study of Structural Phase Transition in Cubic Phase GaN Grown on GaAs (001) with AlGaAs Intermediated Layer

Jamreonta Parinyataramas1, Sakuntam Sanorpim1,2, Chanchana Thanachayanont3, Kentaro Onabe4

1Nanoscience and Technology, Graduate school, Chulalongkorn University
2Department of Physics, Faculty of Science, Chulalongkorn University
3National Metal and Materials Technology Center
4Department of Advanced Materials Science, The University of Tokyo

Abstract: Structural phase transition in cubic GaN layers grown by metalorganic vapor phase epitaxy on GaAs (001) substrates using AlGaAs as an intermediated layer was analyzed by transmission electron microscopy. Roles of the AlGaAs intermediated layer on structural phase transition in nano-scale of cubic GaN layers have been focused. The inserted AlGaAs layer is found to play as a protection layer to prevent the GaAs substrate from thermal decomposition at higher growth temperatures (>900°C) of GaN. This enables us to grow GaN layer on GaAs substrate without a generation of voids at the GaN/AlGaAs interface. On the other hand, the generation of voids, which was observed from the cubic GaN/GaAs/AlGaAs/GaAs (001) structure, was found to stop by the AlGaAs intermediate layer. It is evidenced that, however, the AlGaAs intermediated layer induced the structural phase transition from cubic to hexagonal phases in the GaN top layer. The existence of nano-scale structural phase transition from cubic to cubic/hexagonal mixed phases and their epitaxial relationship in the cubic GaN layer were analyzed through the observation with TEM measurements. This result was confirmed by the results obtained from photoluminescence and Raman scattering measurements.

Key words: Cubic phase GaN, Hexagonal structure, TEM, structural phase transition