Transparent CdO/n-GaN(0001) heterojunction for optoelectronic applications

Abstract

Undoped CdO films were prepared by sol–gel method. Transparent heterojunction diodes were fabricated by depositing n-type CdO films on the n-type GaN (0001) substrate. Current–voltage (I–V) measurements of the device were evaluated, and the results indicated a non-ideal rectifying characteristic with IF/IR value as high as 1.17×103 at 2V, low leakage current of 4.88×10−6A and a turn-on voltage of about 0.7V. From the optical data, the optical band gaps for the CdO film and GaN were calculated to be 2.30eV and 3.309eV, respectively. It is evaluated that interband transition in the film is provided by the direct allowed transition. The n-GaN (0001)/CdO heterojunction device has an optical transmission of 50–70% from 500nm to 800nm wavelength range.