Improved electrical and optical properties of ITO thin films by using electron beam irradiation and their application to UV-LED as highly transparent p-type electrodes

We have investigated the effect of electron beam irradiation to the ITO film on the electrical and optical properties of the ITO film deposited by radio frequency (RF) magnetron sputtering method at room temperature. Electron beam irradiation resulted in a significant decrease in resistivity of the ITO film from 1.3 × 10−3 Ω cm to 3.41 × 10−4 Ω cm. In addition, electron beam irradiation increased the optical band gap of the ITO film from 3.8 eV to 4.3 eV, followed by a transparency of ∼70% at a wavelength of 375 nm. We also fabricated ultraviolet light-emitting diodes (UV-LEDs) by using the ITO p-type electrode with/without electron beam irradiation. The results show that the optical power of the UV-LEDs with electron beam irradiation increased by 58% at 100 mA, when compared to that of the UV-LEDs without electron beam irradiation. The electroluminescence (EL) measurement shows that electron beam irradiation did not change the peak wavelength of the UV-LED, meanwhile it significantly increased the integrated intensity as much as 39.2% at 60 mA. These results strongly suggest that electron beam irradiated ITO film is a good candidate as a p-type electrode for realization of high power UV-LEDs.