Group-III nitrides for optoelectronics
The research activities for wide-gap group-III nitrides cover the
investigation of GaN films with nonpolar surfaces such as the M-plane,
of group-III nitride heterostructures with particular emphasis on (In,Ga)N/GaN quantum wells, and of GaN-based nanostructures. All of these structures are grown by either plasma-assisted (N2 based) or reactive (NH3 based) MBE.
Heteroepitaxial growth
Since native bulk substrates are still not commercially available for any of the group-III nitrides, one is, in most cases, forced to retreat to the use of foreign substrates. The choice of the substrate depends strongly on the actual structure one desires to fabricate. In any case, nucleation, defect formation and residual strain have to be studied for each respective materials combination. The following substrates are routinely used in our research:
- planar growth, C-plane: Al2O3(0001), SiC(0001), GaN(0001), ZnO(0001)
- planar growth, M-plane: γ-LiAlO2(100), SiC(1100)
- nanocolumn growth: Si(111)
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