Growth of p-type a-plane ZnO thin films on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy

Abstract

Non-polar ZnO thin films were grown on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy. The film is ( 11 2 − 0 ) oriented ( a-plane) as identified by the X-ray diffraction pattern. Structural properties are anisotropic and surfaces of films show stripes running along the ZnO [0001] direction. The nonintentionally doped non-polar ZnO film exhibits weak p-type conductivity with a hole concentration of 1.33 × 10 15 cm − 3 , a Hall mobility of 18.7 cm 2 V − 1 s − 1 , and a resistivity of 251.5 Ω·cm, respectively. Near-band-edge emission is dominant in room-temperature photoluminescence while deep level emission is negligible, indicating high optical quality of the p-type non-polar ZnO thin films.