MOVPE of III-Nitrides
MOVPE is a nonequilibrium growth technique which relies on vapor transport of the precursors and chemical reactions of group III alkyls and group ammonia (NH3). Metalorganic (MO) group III sources are either liquid, such as trimethylgallium (TMGa) and trimethylaluminum (TMAl), or solids like trymethylindium (TMIn). These sources are stored in bubblers through which a carrier gas, either nitrogen (N2) or hydrogen (H2), flows. According to the source material, the temperature of the bubbler is properly adjusted to precisely control the vapor pressure over source material. As dopant materials, MO precursors - like Cp2Mg, Cp2Fe and Mn2Cp - and hydrides - like SiH4 - are used.
Due to the fact that MOVPE growth takes place at relatively high pressure (~ 200 mbar), no high vacuum characterization tools like LEED or REED can be used for in-situ monitoring during growth. Therefore, optical characterization techniques such as ellipsometry and reflectometry are most commonly used.
We specialize on the growth of magnetic semiconductors based on GaN - doped with transition metals - grown on 2" c-plane sapphire wafers. All the growth process is in-situ monitored by ellipsometry, which gives us information on the layer thickness and surface roughness.
- Figure: Animation illustrating the principles of MOVPE