Nonalloy Ohmic contact fabrication in a hydrothermally grown n-ZnO (0001) substrate by KrF excimer laser irradiation

Abstract
A nonalloy Ohmic electrode is formed on a hydrothermally grown n-type ZnO substrate by KrF excimer laser irradiation and metal deposition without any impurity doping. Laser irradiation changes the ZnO surface layer to a Zn-rich one with lower sheet resistance than the bulk. The Zn-rich premetallized layer (ZnOx layer, x=0–1) exhibits n+-type conduction, which enables current conduction into the ZnO substrate with Ohmic characteristics. An In/ZnOx contact fabricated by single-pulse laser irradiation with 0.3 J/cm2 on the ZnO substrate has a contact resistance of 7×10−1 Ω cm2. A postheat treatment for 5 min at 300 °C increases the sheet resistance in the premetallized layer, which causes an increase of the contact resistance of the fabricated contact.