Epitaxial growth of ZnO films on lattice-matched ScAlMgO4(0001) substrates

The use of lattice-matched (0.09%) hxagonal oxide substrate, ScAlMgO4, has considerably improved the quality of ZnO films grown by laser molecular-bea m epitaxy. Surface morphology was extremely smooth as represented by atomic ally Bat terraces and 0.26 nm high steps corresponding to the charge neutra l unit of ZnO. Crystallinity was comparable to that of bulk single crystals : full-width at half-maximum value of ZnO(0 0 0 2) rocking curve was 39 arc sec. Optical absorption spectra showed clear splitting of A- and B-exciton lines, indicating low damping. Residual carrier concentration in pristine f ilms was as low as 10(15) cm(-3) with keeping high electron mobility of sim ilar to 100 cm(2)/Vs. Therefore, the ZnO films grown on ScAlMgO4(0001) subs trates can be a starting point for realizing p-type ZnO. In fact, high conc entration (similar to 10(21) cm(-3)) nitrogen can be doped with keeping hig h crystallinity. (C) 2000 Published by Elsevier Science B.V. All rights res erved.