Surface structure of manganese gallium quantum height islands on wurtzite $${\mathbf {GaN}}{\mathbf{(000}}{\bar{\mathbf{1}}})$$ studied by scanning tunneling microscopy

Submonolayer deposition of manganese on gallium-rich, nitrogen polar $$\hbox {GaN}(000\bar{1})$$ surface using radio-frequency nitrogen plasma molecular beam epitaxy leads to the spontaneous formation of manganese gallium into two distinct quantum height islands, 5-layer and 6-layer islands. Atomically resolved scanning tunneling microscopy reveals the atomically flat but unstable 5-layer island surface and the 6-layer island surface with relatively stable row structures. We propose possible surface models for these islands’ surfaces and discuss the clear structural differences explained with strains and partial relaxations. It is found that the 5-layer islands form under lateral strains and a relaxation process leading to non-uniform alternating strains results in the more energetically favorable row structures on the 6-layer island.