École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and Enkris Semiconductor Inc in China used a material structure consisting of five parallel layers of a 10nm aluminium gallium nitride (AlGaN) barrier, 1nm AlN spacer and 10nm GaN channel (Figure 1). The barrier was silicon doped at a partial level of 5x1018/cm3 to enhance conductivity ……（Please refer to http://www.semiconductor-today.com/news_items/2019/jan/ecole_240119.shtml for details）.