Intentional control of n-type conduction for Si-doped AlN and AlXGa1−XN (0.42⩽x<1)

We have obtained n-type conductive Si-doped AlN and ${\mathrm{Al}}_X{\mathrm{Ga}}_{\text{1−X}}\mathrm{N}$ with high Al content $\text{(0.42⩽x<1)}$ in metalorganic vapor phase epitaxy by intentionally controlling the Si dopant density, [Si]. Si-doped AlN showed the n-type conduction when [Si] was less than ${\text{3×10}}^{19}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}.$ When [Si] was more than ${\text{3×10}}^{19}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}},$ it became highly resistive due to the self-compensation of Si donors. This indicates that the self-compensation plays an important role at higher [Si] and determines the upper doping limit of Si for the AlN and ${\mathrm{Al}}_X{\mathrm{Ga}}_{\text{1−X}}\mathrm{N}.$ For $\text{x⩾0.49,}$ the ionization energy of Si donors increased sharply with increasing Al content. These resulted in a sharp decrease in the highest obtainable electron concentration with increasing Al content for the Si-doped ${\mathrm{Al}}_X{\mathrm{Ga}}_{\text{1−X}}\mathrm{N}.$