Isolation of bidimensional electron gas in AlGaN/GaN heterojunction using Ar ion implantation

Gallium nitride (GaN) has superior physical properties suitable for the realization of power switching and high-frequency transistors with better performances than of conventional Si-based devices. In the presence of a bidimensional electron gas (2DEG) close to the interface of AlGaN/GaN heterojunctions, High Electron Mobility Transistors (HEMT) can be fabricated. Ion implantation is an affordable industrial process for the electrical isolation of 2DEG in adjacent AlGaN/GaN HEMTs devices. In this work, we studied the electrical isolation of the 2DEG produced by Ar ion implantation. 2DEG of heterostructure consisting of 18 nm Al0.2Ga0.8N were grown onto carbon doped n-type GaN. The 2DEG has been isolated by Ar ions implantation at 15, 22.5 and 60 keV and fluence of 7 × 1013 cm-2, respectively. The implanted samples were annealed at 600, 750 and 900 °C, respectively, and the thermal stability of the crystal damage and isolation were analyzed by photoluminescence spectroscopy (PL) and capacitance-voltage profiling (CV) through mercury probe analysis. We found that Ar ion implantation at the explored ion energies and fluence produces a significant reduction of the PL peak intensity assigned to radiative recombination at the band edge of GaN, confirming the crystal lattice damage induced by the implant. The PL spectral features are matched by a significant reduction of the 2 DEG carrier density of about six orders of magnitude with respect to the undamaged sample. The reduction of carrier density and, then, the isolation of the 2DEG was found stable at temperature up to 900 °C.