Epitaxial growth of nonpolar ZnO by MOVPE

Abstract

Epitaxial growth characteristics of nonpolar (M-and A-plane) ZnO on M-and R-plane sapphire substrates were investigated. The growth of ZnO along the c-axis direction, which aligns parallel to [2-1-10] and [01-11] directions of M-and R-plane sapphire, is achieved under lower growth temperature and/or VI/II ratio, and this growth direction is preferable for smooth lateral growth. Increasing the growth time, the surface becomes rough on M-plane, while is significantly improved on R-plane sapphire. The growth behaviour on R-plane sapphire can be attributed to the small lattice mismatching along the ZnO c-axis direction and enhanced lateral growth characteristics. From photoluminescence measurements, the appearance of peak at 3.383 eV, which is at higher energy compared to well-known impurity-and/or defect-related peaks, at 10 K suggests the residual strain in ZnO films.

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

“…Moreover, no significant striation reported by others [16,17] can be found on the non-polar ZnO surface, which can be attributed to the heterogeneous of the ZnO grown on R-Al 2 O 3 substrates. When ZnO films are grown on R-plane Al 2 O 3 substrates, they have tendency to grow perpendicular and/or parallel to c-axis direction depending on the growth conditions, such as growth temperature and VI/II mole ratio [17]. Therefore, for the growth conditions we employed, it is possible to have some competition growth along c-axis direction although there is no pronounced ZnO (0 0 0 1) diffraction peak in the XRD patterns.…”

Growth of ZnMgO/ZnO films on r-plane sapphires by pulsed laser deposition

“…In addition to the growth characteristics [3][4][5][6][7][8][9], the growth behavior of Zn 0.8 Mg 0.2 O/ZnO QW structure grown on r-plane sapphire is also reported.…”

Growth of nonpolar (112¯) ZnO films on LaAlO3 (001) substrates

“…1-3 Among them, r-plane sapphire is the most commonly used substrate for a-plane ZnO film deposition. 4,5 Despite the advantages in thermal stability and its low cost, r-plane sapphire inherits a great disadvantage of large anisotropic lattice mismatch ͑ϳ18.2%͒ with ZnO along ͓1100͔, 4 which will greatly reduce the a-plane ZnO crystalline quality by generating a high density of dislocations.…”