A diode with Sb-doped p-type ZnO, MgZnO/ZnO/MgZnO double heterojunction, and undoped n-type ZnO layers was
grown on c-plane sapphire substrate by plasma-assisted molecular-beam epitaxy. Hall effect measurement showed that
the top p-type Sb-doped ZnO layer has a hole concentration of 1×1017cm-3. Mesa geometry light emitting diodes were
fabricated with Au/Ni and Au/Ti Ohmic contacts on top of the p-type and n-type layers, respectively. Strong ultraviolet
emission was achieved, which yielded an output power of 457 nW at 140 mA. The drastic enhancement of the output
power is attributed to carrier confinement in the good-quality intrinsic layer of the double heterojunction. The spatial
distribution of light emission was characterized.