Defect Compensation in Nitrogen-Doped β-Ga2O3 Nanowires: Implications for Bipolar Nanoscale Devices

Nitrogen (N) is a promising candidate currently being pursued for p-type doping in Ga2O3. In this work, the results of detailed investigations into N-doped β-Ga2O3 nanowires using microstructural, chemical, and optical analyses are described. Monoclinic β-Ga2O3 nanowires are grown by chemical vapor deposition using a metallic gallium (Ga) precursor and subsequently doped with N by remote plasma by exploiting their nanoscale cross sections and large surface-to-volume ratios. The N incorporation into β-Ga2O3 is confirmed by X-ray absorption near-edge and Raman spectroscopies without changes in the nanowire morphology. N is found to exist mainly as molecular N2 and N–O chemical states, but a significant portion of N substitutes on oxygen (O) sites. Concurrent temperature-resolved cathodoluminescence measurements of the undoped and N-doped β-Ga2O3 are used to track the temperature dependences of their intrinsic ultraviolet (UV) luminescence and defect-related visible bands from 80 to 480 K. The blue and green bands increase in intensity relative to the UV after N doping; however, their intensity variations with temperature are found to be identical for the undoped and N-doped β-Ga2O3, indicating that these bands originate from existing recombination pathways in Ga2O3 rather than from radiative N-related centers. The enhancement in defect-related luminescence in N-doped β-Ga2O3 is explained by an increase in the concentration of O vacancies as a result of the compensation of NO acceptors.