Formation of ohmic contacts to p-type ZnO

Formation of ohmic contacts to p‐type zinc oxide (ZnO) was studied. The p‐type ZnO samples were grown by metalorganic molecular‐beam epitaxy with diethylzinc, deionized water vapor and monomethylhidrazine and were annealed under oxygen gas ambient at 650 °C or 700 °C for 20 min to activate doped nitrogen acceptors. Although the current‐voltage characteristics measured through gold p‐contacts were not perfectly ohmic, they showed perfectly ohmic properties after rapid thermal annealing (RTA) in the temperature range of 300 to 520 °C for 2 min. The ohmic contact resistivity was measured with the transmission‐line measurement method and it was decreased to approximately 1/64 with increasing the RTA temperature. The minimum contact resistivity of 3.15 × 10−3 Ω cm2 was observed with RTA at 520 °C for 2 min. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)