Characterization of homoepitaxial p-type ZnO grown by molecular beam epitaxy

Abstract

An N-doped, p-type ZnO layer has been grown by molecular beam epitaxy on an Li-diffused, bulk, semi-insulating ZnO substrate. Hall-effect and conductivity measurements on the layer give: $\mathrm{resistivity}{\text{=4×10}}^1\mathrm{\hspace{0.17em}\Omega }\mathrm{cm};$ $\mathrm{hole}\hspace{0.17em}\mathrm{mobility}\text{=2\hspace{0.17em}}{\mathrm{cm}}^2/\mathrm{V} \mathrm{s};$ and hole $\mathrm{concentration}{\text{=9×10}}^{16}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}.$ Photoluminescence measurements in this N-doped layer show a much stronger peak near 3.32 eV (probably due to neutral acceptor bound excitons), than at 3.36 eV (neutral donor bound excitons), whereas the opposite is true in undoped ZnO. Calibrated, secondary-ion mass spectroscopy measurements show an N surface concentration of about ${10}^{19}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}$ in the N-doped sample, but only about ${10}^{17}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}$ in the undoped sample.