Electrical characteristics and trap signatures for Schottky barrier diodes on 4H-SiC, GaN-on-GaN, AlGaN/GaN epitaxial substrates

The forward and reverse current transport mechanisms, temperature dependence of Schottky barrier height (SBH) and ideality factor, barrier inhomogeneity analysis, and trap parameters for Schottky barrier diodes (SBDs) fabricated on 4H-SiC, GaN-on-GaN and AlGaN/GaN epitaxial substrates are reported. High SBH is identified for Ni/4H-SiC (1.31 eV) and Ti/4H-SiC (1.18 eV) SBDs with a low leakage current density of < 10-8 A/cm2 at -200 V. Thermally stimulated capacitance (TSCAP) detects the well-known Z1/2 electron trap at EC – 0.65 eV in both 4H-SiC SBDs, while an additional deep-level trap at EC – 1.13 eV is found only in Ni/4H-SiC SBDs. The vertical Ni/GaN SBD exhibits a promising SBH of 0.83 eV, and two electron traps at EC – 0.18 eV and EC – 0.56 eV are identified from deep-level transient Fourier spectroscopy (DLTFS). A peculiar two-diode model behaviour is detected at Metal/GaN/AlGaN/GaN interface of high-electron mobility transistor (HEMT); the first diode (SBH-1 of 1.15 eV) exists at the standard Metal/GaN Schottky junction, whereas the second diode (SBH-2 of 0.72 eV) forms due to the energy difference between the AlGaN conduction band and the heterojunction Fermi level. The compensational Fe-doping-related buffer traps at EC – 0.5 eV and EC – 0.6 eV are determined in the AlGaN/GaN HEMT, through the drain current transient spectroscopy (DCTS) experiments.