Two-dimensional electron gas isolation mechanism in Al0.2Ga0.8N/GaN heterostructure by low-energy Ar, C, Fe ion implantation

We report a comparative study of the isolation mechanisms of two-dimensional electron gas (2-DEG) in Al0.2Ga0.8N/GaN heterostructure by room temperature ion implantation with Ar, C or Fe at 15, 20, 18 keV and fluences of 7 x 1013, 1 x 1014, 5 x 1013 cm- 2, respectively. The samples were annealed up to 900 degrees C postimplantation and characterized by X-ray Diffraction, X-ray Photoelectron Spectroscopy, Photoluminescence, Rutherford Backscattering Spectrometry in Channeling mode and Capacitance Voltage profiling. The ion implantation produces unrecoverable crystal lattice damage such as point defects and non-radiative carrier traps level into the band gap of GaN. As a consequence, a decrease in the number of occupied states at the upper side of the valence band of GaN was observed. Moreover, defects accumulation at the near-surface region by annealing at 900 degrees C was observed. Due to the various defects, the concentration of 2-DEG carriers, after ion implantation, for all three ions investigated, is reduced from 1019-1020 to less than 1013 --1014 cm-3. The 2-DEG isolation was stable up to 900 degrees C for all three ions, while the non-radiative defects and carrier traps produced were slightly more stable in the case of Fe implantation. The reduction of carrier concentration is responsible for the isolation of 2-DEG.