Structural, Chemical and Electrical Properties of Au/La2O3/n-GaN MIS Junction with a High-k Lanthanum Oxide Insulating Layer

This paper demonstrates the role of high-k La2O3 on the electrical performance of the Au/n-GaN Schottky junction (SJ) as an insulating layer between the Au and n-GaN films. First, the La2O3 is deposited on a n-type GaN surface by e-beam technique and analysed for its structural and chemical properties with x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) approaches. XRD and XPS results confirmed the growth of La2O3 on the n-GaN surface. Then, the Au/La2O3/n-GaN metal/insulator/semiconductor (MIS) junction is fabricated and analysed for its electrical properties and compared with the SJ electrical results. The MIS junction exhibits a good rectifying nature with a low leakage current compared to the SJ. Experimental findings reveal a higher barrier height obtained for the MIS junction than the SJ, suggesting that the barrier height is altered by the La2O3 insulating layer. Also, the barrier heights are estimated by Cheung's, Norde functions and (S)-V plot, and the values are nearly matched with each other, indicating the techniques used here are valid. The extracted interface state density (N-SS) of MIS junction is lower than the SJ, implying the La2O3 insulating layer plays a vital role in the decreased N-SS. Experimental findings confirmed that the Schottky emission governs the reverse current in SJ. However, for the MIS junction, the Poole-Frenkel and Schottky emissions are the dominant current conduction mechanisms in the lower and higher bias regions.