Heterojunctions have been prepared by the reactive rf, sputter deposition ofnhyphen;ZnO on sputterhyphen;etchednhyphen; andphyphen;type silicon substrates. Measurements of conductance show typical lowhyphen;reverse breakdown at 18ndash;25 V and forward currents of 2ndash;10 mA at 3 V, bothnhyphen;nandphyphen;ndiodes rectify. At low forward bias, 0ndash;0.3 V, both types of diode have characteristics of the formI=I0lsqb;exp(qVA/bgr;kT)minus;1rsqb; with large ideality factors bgr; close to 5 fornhyphen;nand 7 forphyphen;njunctions. In the range 0ndash;100thinsp;deg;C bgr; varies by only 15percnt; in each case. Film series resistance predominates above 0.5 V with resistivities close to those measured transversely for films on insulating substrates. A model of highly doped ZnO crystallites with macroscopic mobility controlled by intergranular barriers is coupled with an interface state dominated junction band profile to account for these results.
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