1. Growth and impurity characterization of AlN on (0001) sapphire grown by spatially pulsed MOCVD
- Author
-
Michael Wraback, Roy B. Chung, Ryan Enck, Lee E. Rodak, Meredith Reed, and Anand V. Sampath
- Subjects
010302 applied physics ,Materials science ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,Surfaces and Interfaces ,Chemical vapor deposition ,Surface finish ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Oxygen ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Impurity ,0103 physical sciences ,Materials Chemistry ,Sapphire ,Growth rate ,Metalorganic vapour phase epitaxy ,Electrical and Electronic Engineering ,0210 nano-technology ,Carbon - Abstract
The reduction of undesirable gas phase reaction between trimethylaluminum and NH3 was achieved by spatially separating the precursors using N2 purge line during AlN growth by metal organic chemical vapor deposition (MOCVD). Under this condition, it was shown that the growth pressure has a strong impact on the surface morphology independent of pre-reaction. For 0.8-μm-thick AlN grown on (0001) sapphire substrates, increasing pressure from 200 to 500 Torr drastically increased a root-mean-squared surface (r.m.s.) roughness from 0.48 to 33 nm. This morphological change was previously attributed to the pre-reaction. Less pre-reaction also allowed us to investigate the pressure dependence of impurity (carbon and oxygen) incorporation in AlN as the growth rate was no longer affected by the pressure. Unlike GaN, the carbon level almost doubled with increasing pressure from 200 to 500 Torr. By optimizing the surface morphology (r.m.s. roughness from 33 to 0.62 nm) at 500 Torr, the carbon concentration in AlN decreased from 5 × 1018 to 7 × 1017 cm−3. Although there was no improvement in the structural quality, this uniquely designed MOCVD could further improve the material quality of AlN by reducing the impurity level.
- Published
- 2016