© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.pss-rapid.com pss Phys. Status Solidi RRL 6, No. 3, 114–116 (2012) / DOI 10.1002/pssr.201105508 Single domain nonpolar (13 4 0) ZnO on (114) LaAlO 3 Yen-Teng Ho, Wei-Lin Wang, Chun-Yen Peng, Jr-Sheng Tian, Yi Sen Shih, Tzu-Chen Yen, and Li Chang * Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan Received 2 November 2011, revised 16 December 2011, accepted 19 December 2011 Published online 29 December 2011 Keywords domains, non-polar ZnO, LaAlO 3 , pulsed laser deposition * Corresponding author: e-mail lichang@nctu.edu.tw, Phone: 886-3-5731615, Fax: 886-3-5724727 © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction Zinc oxide (ZnO), with high direct band gap (3.3 eV at 300 K) and wurtzite structure, is a promising semiconductor for light emitting devices thanks to its high exciton binding energy (~60 meV) which allows for high ultraviolet lasing efficiency even above room temperature [1]. It is well known that ZnO of wurtzite structure has strong polarization along the c-direction which is the common growth direction of high-quality epi- taxial ZnO films in devices. As a result, c-ZnO devices suffer from the quantum confined Stark effect (QCSE) to reduce the internal quantum efficiency for light emission which has already been known for c-GaN devices [2, 3]. Therefore, it is desirable to grow ZnO in nonpolar orienta- tions such as a-plane and m-plane to avoid the QCSE [4–6]. Heteroepitaxial growth of nonpolar ZnO is of great in- terest due to expensive ZnO wafers. Growth in a-plane (1120) and m-plane (10 10) on various substrates has already been presented using in many studies [7, 8]; how- ever, it remains as a challenge due to lack of lattice- matched substrate. To improve the crystalline quality of nonpolar ZnO, a suitable substrate of inherently good thermal stability and small lattice mismatch with ZnO is highly required. LaAlO 3 (LAO) is widely used as substrate in epitaxial growth of functional oxide thin films. 4-inch sized wafers are commercially available at relatively low cost. It is ex- pected to be an excellent candidate of substrate for oxide growth. We have previously demonstrated that (001) and (112) LAO substrate can be used to grow a-plane [9] and m-plane ZnO [10], respectively. However, nonpolar a-plane ZnO thin films grown on (001) LAO consist of two types of domains perpendicular to each other due to the symmetric atomic configuration on the surface of LaAlO 3 substrate [9, 11, 12]. The domain boundaries in the a-plane ZnO induce more defects which may deteriorate the optical properties, such that (001) LAO is not an ap- propriate substrate for nonpolar ZnO growth in practical applications. In this Letter, we report that the growth of single do- main nonpolar ZnO can be achieved on (114) LAO sub- strate. Comparing with (001) LAO, (114) plane can be re- garded as a miscut (001) plane in ~ 19.47° from [110] to [1 11] direction, as illustrated in Fig. 1(a). Figure 1(b) shows that (114) LAO provides an asymmetric atomic con- figuration based on the crystallography of psudo-cubic LAO (a 0 = 0.3791 nm). An unconventional nonpolar plane (13 4 0) ZnO epitaxial film was grown on a 2-inch (114) LaAlO 3 (LAO) substrate by pul- sed laser deposition. Reflection high energy electron diffrac- tion (RHEED) patterns of the grown ZnO surface demon- strate single crystalline characteristics with the orientation inclined with the a-axis. Atomic force microscopy (AFM) shows that the grown ZnO film exhibits a stripe-like surface morphology with the longitudinal direction parallel to the c-axis. Cross-sectional transmission electron microscopy (TEM) with selected area electron diffraction (SAED) was used to characterize the microstructure and to determine the growth plane of ZnO grown film as (13 4 0). In addition, XRD pole-figure measurements confirm the single domain growth of (13 4 0) ZnO on (114) LAO. Room temperature photolumi- nescence spectra of the ZnO film measured across the sub- strate show the same near band edge emission peak at 3.29 eV, indicating that the nonpolar (13 4 0) ZnO film has excellent uniform optical properties.