Electrical and Structural Properties of All-Sputtered Al/SiO2/p-GaN MOS Schottky Diode

The all-sputtered Al/SiO2/p-GaN metal-oxide-semiconductor (MOS) Schottky diode was fabricated by the cost-effective radio-frequency sputtering technique with a cermet target at 400 degrees C. Using scanning electron microscope (SEM), the thicknesses of the electrodes, insulator SiO2 layer, and p-GaN were found to be similar to 250 nm, 70 nm, and 1 mu m, respectively. By Hall measurement of a p-Mg-GaN film on an SiO2/Si (100) substrate at room temperature, the hole's concentration (N-p) and carrier mobility (mu) were found to be N-p = 4.32 x 10(16) cm(-3) and mu = 7.52 cm(2).V-1.s(-1), respectively. The atomic force microscope (AFM) results showed that the surface topography of the p-GaN film had smoother, smaller grains with a root-mean-square (rms) roughness of 3.27 nm. By I-V measurements at room temperature (RT), the electrical properties of the diode had a leakage current of similar to 4.49 x 10(-8) A at -1 V, a breakdown voltage of -6 V, a turn-on voltage of similar to 2.1 V, and a Schottky barrier height (SBH) of 0.67 eV. By C-V measurement at RT, with a frequency range of 100-1000 KHz, the concentration of the diode's hole increased from 3.92 x 10(16) cm(-3) at 100 kHz to 5.36 x 10(16) cm(-3) at 1 MHz, while the Fermi level decreased slightly from 0.109 to 0.099 eV. The SBH of the diode at RT in the C-V test was higher than in the I-V test because of the induced charges by dielectric layer. In addition, the ideality factor (n) and series resistance (R-s) determined by Cheung's and Norde's methods, other parameters for MOS diodes were also calculated by C-V measurement at different frequencies.