Growth kinetics of O-polar BexMgyZn1-x-yO alloy: Role of Zn to Be and Mg flux ratio as a guide to growth at high temperature
Abstract
We studied the effect of the substrate temperature, in the range from 450 °C to 500 °C, on the required Zn to (Be + Mg) flux ratio for plasma-assisted molecular beam epitaxy growth of O-polar BexMgyZn1-x-yO on (0001)-GaN/sapphire templates. Achievement of single-crystalline BexMgyZn1-x-yO with improved optical and structural qualities required relatively high substrate temperatures, which necessitated the Zn to (Be + Mg) flux ratio to be increased from 3.9 at 450 °C to 8.3 at 500 °C. This resulted in a reduction of Mg incorporation from 25% to 15% for a fixed Be content of ∼3%. With increasing Zn to (Be + Mg) ratio, 15 K photoluminescence energy for the dominant emission remained unchanged at around 3.75 eV and 3.55 eV for the samples grown at 475 °C and 500 °C, respectively. These findings readily suggest a kinetic limitation of Mg and Be incorporation into wurtzite BexMgyZn1-x-yO lattice, resulting in the formation of second phase due mainly to the enhanced surface mobility of Mg adatoms and, therefore, an increase in the probability of the formation of Mg-rich clusters. An increase in the in-plane lattice parameter, deduced from the Reflection High Energy Electron Diffraction, at the onset of the phase segregation suggests the formation of the wurtzite phase MgO rich alloy(s).
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- May 10, 2017
- Source ID
- 10.1063/1.4983096
Entities
People
- H. Morkoc
- I. Altuntaş
- Md. Barkat Ullah
- S. Hafiz
- T. Nakagawara
- V. Avrutin
- Ümit Özgür
Organizations
- Air Force Office of Scientific Research
- Sivas Cumhuriyet University
- Virginia Commonwealth University