The role of Cu-doping in DLC interlayers on the electrical parameters of MIS-type Schottky devices: A Capacitance-Conductance analysis

This study investigates the influence of copper (Cu) doping in diamond-like carbon (DLC) interlayers on the temperature-dependent electrical characteristics of MIS-type Schottky devices (SDs). Two structures were fabricated: a pure DLC interlayered device (SD1) and a Cu-doped DLC interlayered device (SD2). Capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements were carried out over the 80–410 K temperature range to extract key electrical parameters, including series resistance (RS), interface state density (NSS), and Schottky barrier height (ΦB). The Cu-doped device exhibits consistently lower and more stable real series resistance, with RS decreasing from ∼90 Ω at low temperatures to ∼55–60 Ω at elevated temperatures, while the pure DLC device shows significantly higher Rs values and stronger temperature dependence. Moreover, SD2 demonstrates a more regular temperature evolution of ΦB, whereas SD1 displays more complex behavior. Cu incorporation also reduces NSS from the order of ∼1012 eV-1 cm−2 to below ∼5 × 1011 eV-1 cm−2 and improves the symmetry and linearity of the C-V and 1/C2-V characteristics. A distinct thermally activated NSS feature near 300 K indicates Cu-related interfacial trap dynamics. Arrhenius analysis of the temperature-dependent interface state density further reveals shallow activation energies (∼0.036–0.07 eV) for the pure DLC device, while a higher activation energy (∼0.189 eV) observed for the Cu:DLC structure indicates deeper Cu-induced trap states that become thermally activated near the 230–290 K region. These findings highlight Cu-doped DLC interlayers as an effective route to enhance interfacial quality and thermal stability in MIS-type Schottky devices.