Nitride Semiconductor is an extremely important semiconductor family, has a wide range of modern applications, including optoelectronic devices, new generation communication device and power electronics. Doping is an important method toengineer new and improved properties of semiconductor. However, todate the nature of C doped GaN, especially the lattice site occupation, is not yet well understood. It becomes one of the most problems in the research of Nitride Semiconductor. Prof. Yang and Sheng from Peking University, by using the variable-angle and polarized infrared reflectance spectroscopy technique on infrared beamline at NSRL, provide unambiguous evidence of the substitutionalC atoms occupying the N site with a −1 charge state in GaN and therefore bring essential information to along-standing controversy. This result would be a universal approachfor identification of the lattice sites of C in other compoundsemiconductors such as AlN, BN, ZnO,etc. This work was published in Physical Review Letters (2018, 121, 145505).

(a)-(b)Infrared reflectance spectra of C doped GaN in the different polarization. (c) Relationship between Intensity  and polarization angle for ω1, ω1,and A1(LO) vibrational modes.