  The lattice mismatch between AlGaN and AlN substrates limits the design and
efficiency of UV LEDs, but it can be mitigated by the co-incorporation of
boron. We employ hybrid density functional theory to investigate the
thermodynamic, structural, and electronic properties of BAlGaN alloys. We show
that BAlGaN can lattice match AlN with band gaps that match AlGaN of the same
gallium content. We predict that BAlGaN emits transverse-electric polarized for
gallium content of ~45% or more. Our results indicate that BAlGaN alloys are
promising materials for higher efficiency UV optoelectronic devices on bulk AlN
substrates.
