Benefits of homoepitaxy on the properties of nonpolar (Zn,Mg)O/ZnO quantum wells on a-plane ZnO substrates

Abstract

We report on the properties of nonpolar (Zn,Mg)O/ZnO quantum wells (QW) homoepitaxially grown by molecular beam epitaxy on a-plane ZnO substrates. We demonstrate a drastic improvement of the structural properties. We compare the photoluminescence properties of nonpolar homoepitaxial QWs and nonpolar heteroepitaxial QWs grown on sapphire and show that the reduction in structural defects and the improvement of surface morphology are correlated with a strong enhancement of the photoluminescence properties: reduction in full width at half maximum, strong increase in the luminescence intensities and their thermal stability. The comparison convincingly demonstrates the interest of homoepitaxial nonpolar QWs for bright UV emission applications.

Optical properties of ZnO/(Zn, Mg)O quantum wells

“…with the polar c-direction of ZnO lying in the growth plane. Wide ZnO/(Zn, Mg)Obased QWs without QCSE have been successfully grown on the a-plane (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) [13,22,23] or the m-plane (10-10) [24,25].…”

“…To grow ZnO and its related alloys, other substrates such as SCAM, Si(111), and GaN * Correspondence: thierry.bretagnon@univ-montp2.fr have been successfully used since then. Optical and structural properties were recently improved when the ZnO/(Zn, Mg)O heterostructures were grown by MBE using ZnO substrates [16].…”

Light polarization sensitive photodetectors with m- and r-plane homoepitaxial ZnO/ZnMgO quantum wells

“…This problem can be fully overcome by using nonpolar orientations, such as a-and mplane, where the c-axis lays in-plane and where the electric field along the growth direction is zero. 1 Indeed, ZnO/ (Zn,Mg)O QWs with excellent optical and structural characteristics have been demonstrated with homoepitaxy on non-polar ZnO substrates. [1][2][3] Besides, in semipolar orientations, such as r-plane where the c-axis forms a given angle with the normal to the growth plane, 3 it can be partially reduced.…”

“…1 Indeed, ZnO/ (Zn,Mg)O QWs with excellent optical and structural characteristics have been demonstrated with homoepitaxy on non-polar ZnO substrates. [1][2][3] Besides, in semipolar orientations, such as r-plane where the c-axis forms a given angle with the normal to the growth plane, 3 it can be partially reduced. Nonpolar and semipolar orientations have an additional benefit for certain photodetection applications, because their low crystal symmetry causes a strong optical anisotropy for the excitonic transitions from the three separate p-like valence bands to the s-like conduction band (transitions typically labelled A, B and C excitons).…”

“…Using these substrates, which are available in different plane orientations, lattice-matched homoepitaxial layers can be grown with improved characteristics, including lower threading dislocations densities or lower residual carrier concentrations. [1][2][3] The use of homoepitaxial layers is probably the most promising path to take full advantage of the high ZnO exciton binding energy for optoelectronic devices. Among these devices, photodetectors with unipolar carrier transport (such as Schottky and metal-semiconductor-metal photodiodes) avoid the inherent difficulties with p-type doping in ZnO, 4 allowing access to UV photodetection with good figures of merit.…”