Research of Ohmic and Schottky Contact to n-type ZnO
|Course||Materials Science and Engineering|
|Keywords||specific contact resistance CTLM Schottky transformation Schottkycontact|
ZnO is a promising semiconductor with a direct wide band gap of3.37eV and a large exciton binding energy of60meV at room temperature. It is considered to be a good material for LEDs, LDs, ultraviolet detector, FET and so on. The realization of these devices depends on the electrode of ZnO material. Then, it is important to prepare high quality electrode for ZnO.We utilized n-type Al-doped ZnO thin films prepared by PLD (Pulsed laser deposition), discovered the Ohmic contact to ZnO and optimized the electrodes at the same time. The work included:1. Based on CTLM (Circular transmission line model) model, prepared a new electrode Ti/Ni/Ti/Au by lithographic process, and annealed samples at the range of200-700℃. Finally, we obtained the minimum specific contact resistance of6.69X10-5Ωcm2at500℃. And we found a tendency of gradual Schottky transformation at high temperature.2. According to the analysis of SIMS from Ti/Ni/Ti/Au electrode, we optimized the electrode into Al/Ni/Al/Au, and gained the lowest specific contact resistance of8.47X10-5Ωcm2at400℃. The electrode did not change to Schottky contact at the range of200～800℃annealing. Then, Al/Ni/Al/Au works better than Ti/Ni/Ti/Au for Al doped ZnO thin films at high temperature.Meanwhile, according to the character of tansforming from Ohmic contact into Schottky contact for Ti/Ni/Ti/Au electrode, we investigated Schottky contact for n-type ZnO thin films prepared by MOCVD (Metal organic chemical vapor deposition). After the treatment of H2O2, we gained high quality Ni/Au Schottky contact electrode.