Ni/Au与N掺杂p型ZnO的欧姆接触

研究了Au,In,Ni/Au三种不同金属膜与N掺杂p型ZnO的接触特性,发现Ni/Au双层膜更适合作为其欧姆电极材料,并比较了不同气氛和不同温度退火对Ni/Au电极的影响.发现在O₂中退火电极性能发生蜕变,而在N₂中退火性能得到改善.指出即使在N₂中退火,退火温度的选择也是至关重要的,本实验在400℃,氮气气氛下退火150s,得到了较好的欧姆接触特性.

Ni/Au Contact to N-doped p-type ZnO

ZnO is a direct wide-band-gap(3.37 eV)semiconductor.It has attracted considerable attention as a potential candidate material for gas sensors,transparent electrode and surface acoustic wave deices,especially for ultraviolet light-emitting diodes(LEDs)and laser diodes(LDs).However,for ultimately fabricating ZnO-based optoelectronic devices,the performance of the contacts to ZnO is attracting more and more attention.This is because a good ohmic contact allows lower operating voltage and minimizes dissipation of power,while a poor ohmic property leads to poor device performance and eventually device failure.Compared with that to n-type ZnO,the fabrication of ohmic contacts to p-type ZnO is more difficult since the work function of p-type ZnO is higher than that of single metal.The contact properties of Au,In,Ni/Au to N-doped p-type ZnO films grown by MBE method were reported.The zinc(Zn)source was supplied by evaporating metal zinc with 99.999 9% through a Knudsen effusion cell.NO gas activated by an Oxford Applied Research r.f.(13.56 MHz)plasma source with a power of 300 W was used as both N and O source.Compared with Au and In contacts,Ni/Au contact is more suitable to form stable ohmic contact to p-type ZnO.The contacts behavior of Ni/Au after annealing under N₂ and O₂ ambient were given.It was found Ni/Au contact gave a degenerative behavior after rapid thermal annealing(RTA)under O₂ ambient at the temperature of 300℃ for 150 s,while an improved contact behavior was obtained after RTA under N₂ in the same temperature for 150 s.The dependence of Ni/Au contact on the annealing temperature under N₂ gas ambient was investigated.With the increase of the annealing temperature,the resistances of Ni/Au contacts decrease firstly and then increase.In this experiment,after RTA at 400℃ under N₂ for 150 s,the Ni/Au contact gives a better ohmic characteristic,and the contact resistivity is about 0.8 Ω·cm².