Improvement of p-type conductivity in Al-rich AlGaN substituted by MgGaδ-doping (AlN)m/(GaN)n (m≥n) superlattice

The challenge of p-type doping in Al-rich AlGaN is investigated based on first-principles calculations. We find that the p-type conductivity can be improved by replacing Al-rich AlGaN with MgGaδ-doping (AlN)m/(GaN)n (m ≥ n) superlattice (SL). The formation energy Ef is the lowest and acceptor activation energy EA is the smallest for Mg substituting Ga in the SL. The EA increases if the doping position moves from GaN to AlN layer. Moreover, EA decreases with increasing the number of GaN monolayers. The EA can be reduced from 0.48 eV in AlN to 0.26 eV in (AlN)5/(GaN)1, 0.25 eV in (AlN)1/(GaN)1, 0.24 eV in (AlN)4/(GaN)2 and 0.22 eV in (AlN)3/(GaN)3 SLs. This will lead to a high hole concentration in the order of 1018 cm−3 at room temperature, which is favorable for AlGaN-based deep ultraviolet optoelectronic devices.