Submicron Size Schottky Junctions on As-Grown Monolayer Epitaxial Graphene on Ge(100): A Low-Invasive Scanned-Probe-Based Study

Abstract

We report on the investigation of the Schottky barrier (SB) formed at the junction between a metal-free graphene monolayer and Ge semiconductor substrate in the as-grown epitaxial graphene/Ge(100) system. In order to preserve the heterojunction properties, we defined submicron size graphene/Ge junctions using the scanning probe microscopy lithography in the local oxidation configuration, a low-invasive processing approach capable of inducing spatially controlled electrical separations among tiny graphene regions. Characteristic junction parameters were estimated from I–V curves obtained using conductive-atomic force microscopy. The current–voltage characteristics showed a p-type Schottky contact behavior, ascribed to the n-type to p-type conversion of the entire Ge substrate due to the formation of a large density of acceptor defects during the graphene growth process. We estimated, for the first time, the energy barrier height in the as-grown graphene/Ge Schottky junction (φB ≈ 0.45 eV) indicating an n-type doping of the graphene layer with a Fermi level ≈ 0.15 eV above the Dirac point. The SB devices showed ideality factor values around 1.5 pointing to the high quality of the heterojunctions.

Camphor-Based CVD Bilayer Graphene/Si Heterostructures for Self-Powered and Broadband Photodetection

“…Therefore, the dark current under a low reverse bias (from 0 V to −2 V) is much lower than under a low forward bias (form 0 V to +2 V), as shown in Figure 4 b,c. It is noteworthy that the SBH tunable behavior of the camphor-based CVD graphene/p-Si heterostructure is consistent with the numerous study results of the conventional CVD bilayer graphene/Si heterostructures reported previously [ 58 , 59 , 60 , 61 , 62 , 63 ].…”

Tuning the Doping of Epitaxial Graphene on a Conventional Semiconductor via Substrate Surface Reconstruction

“…Consequently the graphene/Ge system has recently attracted a great deal of interest both in materials science [8][9][10][11] and device physics [12][13][14]. Previous work has demonstrated that the Ge(001) surface forms high-index facets upon graphene synthesis, making the system unsuitable for further processing [12,15,16].…”

“…The location of the vacancy is highlighted by the black circle in Figure 4a,b. As known in the literature [14,[26][27][28][29],…”

“…It has sufficient catalytic activity with respect to the precursor gas, without a disruptive chemical affinity for carbon (in contrast to Si). Consequently, the graphene/Ge system has recently attracted a great deal of interest both in materials science − and device physics. − Previous work has demonstrated that the Ge(001) surface forms high-index facets upon graphene synthesis, making the system unsuitable for further processing. ,, In contrast, such faceting does not occur for the Ge(110) surface, , which can support growth of single-crystal graphene on wafer scale. ,− …”

Direct growth of graphene on Ge(100) and Ge(110) via thermal and plasma enhanced CVD

“…The attractiveness of graphene integration into CMOS technology arises from a wide variety of potential applications, including photodetectors and modulators for the NIR regime 27 − 29 or passivation layers 17 , 30 . Hereby, different Ge platforms, like Ge on Si 31 , 32 or Ge on insulator 33 , 34 are used.…”