Electric‐Field Enhancement of Electron Emission Rates for Deep‐Level Traps in n‐type GaN

Results of a deep‐level transient spectroscopy (DLTS) study of trapping states in Ni/Au Schottky diodes made on Si‐doped GaN layers grown by metal–organic vapor‐phase epitaxy (MOVPE) on highly conductive n‐type Ammono‐GaN substrates are reported. In all as‐grown samples, the DLTS signals due to traps with the activation energies for electron emission ( E em ) of about 0.26 and 0.60 eV (referred to as E1 and E3 traps, respectively) have been detected. It is found that the electric field ( E ) significantly enhances the electron emission rate ( e em ) for the E1 trap, while for the E3 trap the e em ( E ) dependence is not very strong. The e em ( E ) dependence for the E1 trap is found to be characteristic of attractive traps with spherically symmetric square well potential with a radius of about 2.9 ± 0.25 nm. The e em ( E ) dependence for the E3 trap is accounted for by a phonon‐assisted tunneling mechanism. The zero‐ E E em values for both traps are determined. Correlations between the concentrations of the E1 and E3 traps and concentrations of impurities (H, C, Si, O, Mg, and Fe) determined by secondary ion mass spectrometry in the samples are investigated. Charge states and origins of the E1 and E3 traps are discussed.