Dual-Gaussian Schottky barrier distribution in CVD graphene/n-Si diodes from temperature-dependent transport

Abstract

The transformative potential of graphene/Si Schottky junctions for electronic and power-electronic applications stems from their exceptional thermal and chemical resilience compared to conventional metal contacts. In this work, chemical vapor deposition-grown graphene was transferred onto n-type Si to fabricate Schottky barrier diodes, and the structural, morphological, and electronic properties of the graphene were characterized by Raman spectroscopy and ultraviolet photoelectron spectroscopy. The temperature-dependent current–voltage (I–V) characteristics of the fabricated devices were systematically investigated over the temperature range of 80–300 K. At room temperature, the ideality factor and Schottky barrier height (SBH) were determined to be 2.84 and 0.51 eV, respectively, based on the thermionic emission theory. An ideality factor significantly exceeding unity indicates that charge transport is not governed exclusively by thermionic emission, but also involves thermionic field emission and generation–recombination processes. The pronounced temperature dependence of both the ideality factor, decreasing from 7.41 ± 0.19 at 80 K to 2.84 ± 0.17 at 300 K, and the SBH, increasing from 0.17 ± 0.001 eV to 0.51 ± 0.005 eV over the same range, reveals the presence of significant Schottky barrier inhomogeneity at the graphene/silicon interface. The spatial non-uniformity of the barrier height was quantitatively analyzed within the potential fluctuation formalism of Werner and Güttler, assuming a Gaussian distribution of barrier heights. Two distinct temperature regimes were identified: region I (80–140 K) and region II (160–300 K), yielding mean barrier heights ϕm = 0.42 and 0.72 eV, standard deviations σs = 0.10 and 0.05 eV, and Richardson constants A* = 21.2 and 13.8 A cm−2 K−2. The experimentally extracted Richardson coefficients are substantially below the theoretical value for bulk n-type Si (112 A cm−2 K−2), attributed to the finite density of states arising from the linear band dispersion of graphene. The interface trap density, estimated from the excess ideality factor, lies in the range of ∼2.6–9.0 × 1013 eV−1 cm−2 between 300 and 80 K, consistent with amphoteric Pb0-type defects at the Si/SiO2 interface. The series resistance remains nearly constant over most of the investigated temperature range, with a slight reduction observed at higher temperatures. All key electrical parameters were reproduced within approximately 5% across three nominally identical devices, confirming fabrication reliability and interface stability.