Characteristics of unannealed ZnMgO∕ZnO p-n junctions on bulk (100) ZnO substrates

Zn 0.9 Mg 0.1 O ∕ Zn O p-n junctions were grown by pulsed laser deposition at ⩽500°C on bulk n-type, (100), nonpolar, a-plane ZnO substrates. No postgrowth annealing was performed, with the P-doped ZnMgO showing p-type conductivity (hole density ∼1016cm−3, mobility ∼6cm2V−1s−1) in the as-grown state. Front-to-back p-n junctions were fabricated with Ni∕Au used as the p-Ohmic contact and Ti∕Au as the backside n-Ohmic contact. The p contacts showed improved characteristics after annealing up to 400°C, but the n contacts were Ohmic as deposited. The junctions showed rectifying behavior up to 200°C. The forward turn-on voltage was ∼6.5V at 25°C. The simple, low-temperature growth and processing sequence show the promise of ZnO for applications in transparent electronics and UV light emitters.