100‐nm thick single‐phase wurtzite BAlN films with boron contents over 10%

Abstract

Growing thicker BAlN films while maintaining single‐phase wurtzite structure and boron content over 10% has been challenging. In this study, we report on the growth of 100 nm‐thick single‐phase wurtzite BAlN films with boron contents up to 14.4% by MOCVD. Flow‐modulated epitaxy was employed to increase diffusion length of group‐III atoms and reduce parasitic reactions between the metalorganics and NH3. A large growth efficiency of ∼2000 μm mol−1 was achieved as a result. Small B/III ratios up to 17% in conjunction with high temperatures up to 1010 °C were utilized to prevent formation of the cubic phase and maintain wurtzite structure.

Investigation of Boron Containing AlN and AlGaN Layers Grown by MOVPE

“…Furthermore, these needles do not form a completely coalesced layer, which is also obvious in the plan view image. The column diameter varies from 20 to 40 nm, which is in good agreement with grain sizes for B‐III‐N observed in literature …”

“…Recent studies have shown that B‐III‐N based crystals can exhibit lattice twinning or tilting . SAED measurements (Figure a–d) were carried out to prove the absence of lattice twinning and polycrystalline growth.…”

“…The column diameter varies from 20 to 40 nm, which is in good agreement with grain sizes for B-III-N observed in literature. [7,16] Investigations of the coalescence regions of the grains with HRTEM ( Figure 3) reveal the presence of amorphous material between the crystalline columns, even better evidenced by fast Fourier transformation (FFT) in that area. The plan view and cross section micrographs show columns in the upper part of the AlBN layer.…”

“…Recent studies have shown that B-III-N based crystals can exhibit lattice twinning [15] or tilting. [7] SAED measurements www.advancedsciencenews.com www.pss-b.com (Figure 12a-d) were carried out to prove the absence of lattice twinning and polycrystalline growth. There are no additional diffraction spots apart from the wurtzite AlN in the lower SL region (Figure 12a,b).…”

“…Recent experimental studies show single phase epitaxial growth of AlBN for boron contents up to %10%. [7] However, provided TEM micrographs seem to indicate irregularities in the crystalline structure which might be due to the fact that the solubility limit is reached if not even surpassed, as evidenced by spinodal isotherm calculations where a maximum boron content of 3% for a stable phase in AlN and GaN is predicted for a growth temperature of 1000 C. [8,9] This may be also the reason that up to now we could not find acceptable photoluminescence data of AlBGaN layers even with low B content in the open literature.…”