Band alignment and quality of Al0.6Ga0.4N/AlN films grown on diamond (111) substrate by remote N-plasma assisted MBE

In an attempt to fabricate an n-type Al0.6Ga0.4N film on a p-type diamond (111) substrate, the technique of remote N-plasma assisted MBE was used. Thin AlN layers were grown on boron-doped p-type diamonds to examine band alignment. Al0.6Ga0.4N layers were grown on the AlN layer. The techniques of RHEED, AFM, XPS, XPD, and Hall-measurements were used for the characterization. It was found that the AlN layers are not pure wurtzite but mixed possibly with amorphous Al2O3 region and that the band alignments are favorably modified by the presence of possible amorphous Al2O3. It was further found that the presence of ∼1ML of Si on the substrate diamond surface gives nearly type-I band alignment of amorphous Al2O3 to the substrate. The Al0.6Ga0.4N layers were found in a form of ∼2 nm size grains surrounded possibly by amorphous Al2O3/Ga2O3 regions. The Al0.6Ga0.4N layers were found to be n-type conductive with a very low mobility and the conductivity seems to be derived by thin metallic layers that possibly surrounding Al0.6Ga0.4N grains.