Nonpolar (1120) p-Type Nitrogen-Doped ZnO by Remote-Plasma-Enhanced Metalorganic Chemical Vapor Deposition

Abstract

Nonpolar crystal orientation showed a positive effect on the chemical bonding states of nitrogen-doped ZnO (ZnO:N) for attaining p-type conductivity. Remote-plasma-enhanced metalorganic chemical vapor deposition (RPE-MOCVD) was used to grow nonpolar-and polar-orientated films on R-plane and a-plane sapphires, respectively. Non-polar orientation permitted nitrogen doping as the acceptor mode with lesser donor complexes giving p-type conductivity in both as-grown and annealed conditions. Carbon complexes (C with O) were observed in both orientations with lower binding energy in the nonpolar orientation showing weak complexes in the nonpolar mode. The difference in the mechanism of nitrogen incorporation depending on nonpolar-and polar-oriented growths was explained.

Structural and optical properties of polar and non-polar ZnO films grown by MOVPE

“…It is known that ZnO crystallized in a wurtzite structure contains both polar and non-polar crystallographic planes and the polarity status can determine crucial optical and electrical properties of the films [7,8]. For example, strong spontaneous polarization and piezoelectric polarization along ZnO c-axis in a polar ZnO-based multiple quantum well structure may result in a deterioration of the luminous efficiency similar to that in GaN-based LEDs [9].…”

p-type non-polar m-plane ZnO films grown by plasma-assisted molecular beam epitaxy

“…It is known that ZnO crystallized in wurtzite structure contains both polar and non-polar crystallographic planes and the optical and electrical properties of the films are greatly affected by the polarity-induced effects [2,3]. Generally, most of ZnO-based devices are grown along the polar c-axis direction on c-plane or a-plane sapphire.…”

“…Therefore, in order to construct non-polar ZnO-based light-emitting device, it is indispensable to grow high-quality non-polar ZnO thin films with p-type conductivity. Yet, there are only a few studies dealing with the p-type doping of non-polar ZnO films [3,11]. The fabrication of reliable, stable, and reproducible p-type ZnO has been extensively studied in polar ZnO films.…”

Effects of gallium doping on properties of a-plane ZnO films on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy

“…Nevertheless, sapphire substrates are the most commonly used substrates for the growth of polar and nonpolar ZnO films since bulk ZnO substrates are still expensive. Therefore, most of polar 6-10 and nonpolar 11,12 ZnO films have been grown on sapphire substrates, whereas very few studies were performed on ZnO substrates. 13,14 Impurity incorporation into ZnO lattices induces lattice deformation, forms impurity states in bandgap, and influences the electron transport mechanism, which result in changes in structural, optical, and electrical properties.…”