Structures and stability of polar GaN thin films on ScAlMgO4 substrate: An ab initio-based study

The structures and stability of polar GaN/ScAlMgO4(0001) interfaces are investigated by performing density-functional calculations. On the basis of the calculated interface energies, we find characteristic features of atomic arrangements depending on the polarity of interface. The interface with Ga-adatom is stabilized over the wide range of Ga chemical potential for Ga-polar GaN, while the interface with N-adatom is always stable for N-polar GaN. Furthermore, the interface resulting in Ga-polar films is found to be more stable than that in N-polar films on ScAlMgO4(0001) substrate. The stability of polar GaN/ScAlMgO4 interfaces is interpreted in terms of the formation of stable bonds and charge neutrality at the interface. •The structures and stability of polar GaN/ScAlMgO4(0001) interfaces are investigated by performing density-functional calculations.•The most stable structure is determined using absolute interface energy.•The interface resulting in N-polar films is more stable than that in Ga-polar films on ScAlMgO4(0001) substrate.•The interplay of chemical bonding and charge neutrality at the interface is crucial for GaN/ScAlMgO4(0001) interface.