Effects of Si⁹⁺ ion irradiation on AlGaN double heterostructures were investigated.

Dislocation densities of GaN reduced at liquid nitrogen temperature irradiation.

Variation in phase shift on Al_0.33Ga_0.77N surfaces was measured by EFM.

Capacitance per unit area values of AFM tip-sample surface system were calculated.

Si⁹⁺ irradiations play an important role to tune the energy gap in Al_0.14Ga_0.86N.