MgZnO:P homoepitaxy by pulsed laser deposition: pseudomorphic layer-by-layer growth and high electron mobility

Abstract

ABSTRACT Homoepitaxial ZnO thin films doped with phosphorus (0.01% to 1% P) and/or alloyed with magnesium (1% to 4% Mg) show pseudomorphic growth with compressive or tensile strain in dependence on the dopant concentration. The structural quality of the used O-face Zn O(001) substrates was insp ected by the rocking curves of the symmetric (002) and the skew-symmetric (101) pe aks. Preselection of the substrate batches by the supplier decreased the twist dislocation density and increased the structural hom ogeneity within the batches considerably . TEM cross sections show increasing density of c-plane defects with increasin g phosphorus concentration in the films. ZnO(002) rocking curves of MgZnO:P films on ZnO were as narrow as 27 arcsec with a FWHM of the substrate peak of 23 arcs ec. The in-plane lattice match was confirmed for all dopant concentrations by HR-XRD triple axis scans of the (002) and (101) peaks. The results show the balance between tensile strain induced by Mg and compressive strain by P in ZnO. Two-dimensional growth with terrace-like surface structure is most prominent for th e Mg-alloyed films without P. Hi gh electron mobilities up to 190 cm²/Vs at 300K and up to 800 cm²/Vs at 70 K were found in the homoepitaxial MgZnO:P thin films. Keywords: ZnO thin films, homoepitaxy, MgZnO, P-doped ZnO, dopant activation, pseudomorphic growth, Pulsed Laser deposition, High-resolution X-Ray Diffraction, Hall effect