Field dependent transformation of electron traps in GaN p–n diodes grown by metal–organic chemical vapour deposition

Deep level transient Fourier spectroscopy (DLTFS) has been performed on p–n diodes of GaN. Typical deep level spectra of the various diodes realized on the same wafer demonstrate three electron trap levels, E1, E2 and E3 with activation energies of 0.59, 0.76 and 0.96 eV, respectively below the conduction band. The traps concentration of each level is highly sensitive to the applied electric field during the DLTFS measurements. As a result of repetitive DLTFS scans on the representative diode, the level E2 disappears after the fourth scan, while the associated peak height of the levels E1 and E3 exhibit an overall reduction by a factor of two. We correlate this effect to the transformation of electrically active charged defects into inactive ones under the influence of the electric field, which is increased in the depletion zone by the applied reverse bias. Possible inactivation mechanisms and origins of the observed levels are discussed.