Study of electrically active defects in n-GaN layer

Abstract

Deep level defects in both p +/n junctions and n-type Schottky GaN diodes are studied using the Fourier transform deep level transient spectroscopy. An electron trap level was detected in the range of energies at E c− E t=0.23–0.27 eV with a capture cross-section of the order of 10 −19–10 −16 cm 2 for both the p +/n and n-type Schottky GaN diodes. For one set of p +/n diodes with a structure of Au/Pt/p +–GaN/n–GaN/n + –GaN/Ti/Al/Pd/Au and the n-type Schottky diodes, two other common electron traps are found at energy positions, E c− E t=0.53–0.56 eV and 0.79–0.82 eV. In addition, an electron trap level with energy position at E c− E t=1.07 eV and a capture cross-section of σ n=1.6×10 −13 cm 2 are detected for the n-type Schottky diodes. This trap level has not been previously reported in the literature. For the other set of p +/n diodes with a structure of Au/Ni/p +–GaN/n–GaN/n +–GaN/Ti/Al/Pd/Au, a prominent minority carrier (hole) trap level was also identified with an energy position at E t− E v=0.85 eV and a capture cross-section of σ n=8.1×10 −14 cm 2. The 0.56 eV electron trap level observed in n-type Schottky diode and the 0.23 eV electron trap level detected in the p +/n diode with Ni/Au contact are attributed to the extended defects based on the observation of logarithmic capture kinetics.