A new system for sodium flux growth of bulk GaN: Part I : System development
Loading...
Access rights
openAccess
acceptedVersion
URL
Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This publication is imported from Aalto University research portal.
View publication in the Research portal (opens in new window)
View/Open full text file from the Research portal (opens in new window)
Other link related to publication (opens in new window)
View publication in the Research portal (opens in new window)
View/Open full text file from the Research portal (opens in new window)
Other link related to publication (opens in new window)
Date
2016-12-15
Department
Major/Subject
Mcode
Degree programme
Language
en
Pages
9
Series
Journal of Crystal Growth, Volume 456, pp. 58-66
Abstract
Though several methods exist to produce bulk crystals of gallium nitride (GaN), none have been commercialized on a large scale. The sodium flux method, which involves precipitation of GaN from a sodium-gallium melt supersaturated with nitrogen, offers potentially lower cost production due to relatively mild process conditions while maintaining high crystal quality. We successfully developed a novel apparatus for conducting crystal growth of bulk GaN using the sodium flux method which has advantages with respect to prior reports. A key task was to prevent sodium loss or migration from the growth environment while permitting N2 to access the growing crystal. We accomplished this by implementing a reflux condensing stem along with a reusable capsule containing a hermetic seal. The reflux condensing stem also enabled direct monitoring of the melt temperature, which has not been previously reported for the sodium flux method. Furthermore, we identified and utilized molybdenum and the molybdenum alloy TZM as a material capable of directly containing the corrosive sodium-gallium melt. This allowed implementation of a crucible-free system, which may improve process control and potentially lower crystal impurity levels. Nucleation and growth of parasitic GaN ("PolyGaN") on non-seed surfaces occurred in early designs. However, the addition of carbon in later designs suppressed PolyGaN formation and allowed growth of single crystal GaN. Growth rates for the (0001) Ga face (+c-plane) were up to 14μm/h while X-ray omega rocking (ω-XRC) curve full width half-max values were 731″ for crystals grown using a later system design. Oxygen levels were high, >1019 atoms/cm3, possibly due to reactor cleaning and handling procedures.Description
Keywords
A1. Na flux method, A1. Reactor Design, A2. Growth from high temperature solutions, A2. Sodium flux growth, B1. Bulk GaN, B1. III-Nitrides, B1. Nitrides
Other note
Citation
Von Dollen, P, Pimputkar, S, Alreesh, M A, Albrithen, H, Suihkonen, S, Nakamura, S & Speck, J S 2016, ' A new system for sodium flux growth of bulk GaN : Part I : System development ', Journal of Crystal Growth, vol. 456, pp. 58-66 . https://doi.org/10.1016/j.jcrysgro.2016.07.044