Realization of conductive AlN epitaxial layer on Si substrate using spontaneously formed nano-size via-holes for vertical AlGaN high power FET

Abstract

If vertical AlGaN FET on Si substrate is realized, high power, high voltage FET beyond SiC and GaN FET is obtained due to the high band gap and high breakdown voltage. For realizing vertical AlGaN FET on Si substrate, conductive AlN buffer layer on Si substrate is indispensable, because AlN buffer layer is necessary for growing AlGaN on Si substrate to avoid large size melt-back of Si substrate by Ga source during the growth. However, AlN is known to be a highly insulating material, and preparation of conductive AlN remained to be a challenge. We have successfully realized conductive AlN buffer layer by forming nano-size spontaneous via-holes. The vertical conductivity through AlN is enhanced about 1000-fold by filling conductive n-AlGaN inside the via-holes. Using the conductive via-holes, we have succeeded in fabricating vertical UV-LED emmitting 350nm and vertical UV sensor with responsivity of 150 mA/W at 193nm on Si substrate.