[1] Kumoh Natl Inst Technol, Dept Opt Engn, Gumi 39253, South Korea
[2] King Abdullah Univ Sci & Technol KAUST, Elect & Comp Engn Program, Div Comp Elect & Mathe Sci & Engn CEMSE, Photon Lab, Thuwal 239556900, Saudi Arabia
[3] Univ Sci & Technol China, Sch Microelect, iGaN Lab, Hefei 230026, Anhui, Peoples R China
[4] Chinese Acad Sci, Inst Semicond, Inst Semicond, Beijing 100083, Peoples R China
[5] Univ Chinese Acad Sci, Coll Mat Sci & Optoelect Technol, Beijing 101804, Peoples R China
[6] Univ Aveiro, Inst Telecomun, P-3810193 Aveiro, Portugal
[7] Univ Aveiro, Dept Fis, Campus Santiago, P-3810193 Aveiro, Portugal
[8] Univ Aveiro, i3N, Campus Univ Santiago, P-3810193 Aveiro, Portugal
[9] Int Iberian Nanotechnol Lab, Braga, Portugal
[10] King Abdullah Univ Sci & Technol KAUST, Imaging & Characterizat Core Lab, Thuwal 239556900, Saudi Arabia