Alleviation of fermi-level pinning effect at metal/germanium interface by the insertion of graphene layers

Baek, Seung-heon Chris; Seo, Youngkyun; Oh, Joong Gun; Park, Min Gyu Albert; Bong, Jae Hoon; Yoon, Seong Jun; Seo, Min Hong; Park, Seung-young; Park, Byong‐Guk; Lee, Seok-Hee

doi:10.1063/1.4893668

Cited by 25 publications

(19 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Ge/Co Schottky barrier could be tuned by the number of layers of the inserted graphene. Graphene here has potential as the tunneling barrier for spin injection from Co to Ge …”

Section: Graphene Contact To Conventional Semiconductorsmentioning

confidence: 99%

See 1 more Smart Citation

Contacts between Two- and Three-Dimensional Materials: Ohmic, Schottky, and p–n Heterojunctions

et al. 2016

View full text Add to dashboard Cite

After a decade of intensive research on two-dimensional (2D) materials inspired by the discovery of graphene, the field of 2D electronics has reached a stage with booming materials and device architectures. However, the efficient integration of 2D functional layers with three-dimensional (3D) systems remains a significant challenge, limiting device performance and circuit design. In this review, we investigate the experimental efforts in interfacing 2D layers with 3D materials and analyze the properties of the heterojunctions formed between them. The contact resistivity of metal on graphene and related 2D materials deserves special attention, while the Schottky junctions formed between metal/2D semiconductor or graphene/3D semiconductor call for careful reconsideration of the physical models describing the junction behavior. The combination of 2D and 3D semiconductors presents a form of p-n junctions that have just marked their debut. For each type of the heterojunctions, the potential applications are reviewed briefly.

show abstract

“…The Ge/Co Schottky barrier could be tuned by the number of layers of the inserted graphene. Graphene here has potential as the tunneling barrier for spin injection from Co to Ge …”

Section: Graphene Contact To Conventional Semiconductorsmentioning

confidence: 99%

“…Graphene here has potential as the tunneling barrier for spin injection from Co to Ge. 114 Gallium Nitride. As a wide band gap (3.4 eV) semiconductor, GaN has been widely used in bright light-emitting diodes (LEDs).…”

Section: Graphene Contact To Conventional Semiconductorsmentioning

confidence: 99%

Contacts between Two- and Three-Dimensional Materials: Ohmic, Schottky, and p–n Heterojunctions

et al. 2016

View full text Add to dashboard Cite

show abstract

“…The scalable integration of graphene onto semiconductor platforms is an important step toward utilizing the exceptional structural, electronic, thermal, and mechanical properties of graphene in conventional semiconductor technologies. In particular, graphene/Ge heterostructures have emerged as an exciting materials system for state-of-the-art electronics for several reasons: (1) graphene supported on Ge can simultaneously exhibit high charge carrier mobility and concentration; 1 (2) hybrid photodetectors based on graphene/Ge Schottky barrier junctions can exhibit high responsivity; 2,3 (3) the insertion of graphene between metals and Ge can alleviate Fermi-level pinning to improve contact resistance; 4 (4) the insertion of graphene between dielectrics and Ge can suppress formation of interfacial defect states to reduce hysteresis and leakage current in Ge-based devices; 5 (5) graphene can decouple interlayer bonding to grow nonlatticematched III−V semiconductors directly on Ge; 6 and (6) chemical templates consisting of alternating stripes of graphene and Ge can direct the assembly of block copolymers into nanoscale patterns. 7 These applications, however, are sensitive to the structural, electronic, and chemical nature of the graphene/Ge interface.…”

Section: Introductionmentioning

confidence: 99%

Passivation of Germanium by Graphene for Stable Graphene/Germanium Heterostructure Devices

Jacobberger

Dodd

Zamiri

et al. 2019

ACS Appl. Nano Mater.

View full text Add to dashboard Cite

Graphene grown directly on Ge via chemical vapor deposition (CVD) can passivate the underlying Ge surface, preventing its oxidation in ambient air for at least months. However, the factors that govern oxidation of Ge coated with graphene have not been elucidated. We investigate the effect of graphene synthesis parameters and Ge surface orientation on passivation of Ge and correlate these data with the density and type of defects in graphene. Oxidation of Ge can be reduced by increasing the H2:CH4 flux ratio or decreasing the growth rate, which decrease the density of atomic-scale defects, such as point defects and grain boundaries, in graphene. Oxidation of graphene is concomitant with oxidation of Ge and occurs more readily when the density of atomic-scale defects is relatively high. Passivation of Ge, however, depends more strongly on Ge surface orientation, as Ge(110) oxidizes significantly less than Ge(001) or Ge(111), even at the same graphene defect density. These results provide a pathway for engineering high-quality graphene films on Ge, which may enable improved passivation of Ge and direct integration of graphene-based or hybrid graphene/Ge heterostructure devices on conventional semiconductor platforms.

show abstract

“…Nevertheless, since the interface layer resistance is added, the direct metal=Ge interface with a low SBH is more preferable from the viewpoint of contact resistance reduction. With respect to the direct metal=Ge interface, it has recently been reported that the SBHs at epitaxial Fe 3 Si, 18) α-TiGeN, 19) epitaxial Mn 5 Ge 3 , 20) epitaxial NiGe 2 , 21) graphene, 22) and Sn 23) =n-Ge interfaces are relatively low, which deviates from the trend of strong FLP. 7,8) Some of them 18,20,21,23) considered that the FLP on Ge might not be determined by an intrinsic but extrinsic origin.…”

mentioning

confidence: 95%

Reexamination of Fermi level pinning for controlling Schottky barrier height at metal/Ge interface

Nishimura

Yajima

Toriumi

2016

Appl. Phys. Express

View full text Add to dashboard Cite

The element metal/germanium (Ge) interface exhibits a strong Fermi level pinning (FLP), which is usually characterized on the basis of Ge side semiconductor properties. In this work, we demonstrate that metal properties significantly affect the Schottky barrier height (SBH) on Ge. Metallic germanides show both FLP alleviation and a clear substrate orientation dependence of SBH on Ge, despite the nearly perfect FLP and very slight orientation dependence in the element metal case. As a result, ohmic characteristics are observed at germanide/n-Ge (111) junctions. The metal properties required to alleviate the FLP on Ge are also discussed. © 2016 The Japan Society of Applied Physics G ermanium (Ge) is one of the promising semiconductor materials for high-performance complementary metal-oxide-semiconductors (CMOSs) in the next generation owing to its high electron and hole mobilities. Recently, high electron mobility in Ge n-channel metal-insulation-semiconductor field-effect transistors (n-MISFETs) with a sub-nm equivalent oxide thickness gate stack has been demonstrated, owing to appropriate gate stack designing, [1][2][3][4] in addition to the high hole mobility in Ge p-MISFET, which has already been reported. 5,6) Therefore, the most serious challenges for realizing practical scaled Ge CMOS are currently the reduction in parasitic resistance and the suppression of off-state leakage at the source=drain of MISFETs. In particular, to reduce the contact resistance at the metal=Ge interface, a reduction in Schottky barrier height (SBH) at the interface is definitely required. However, the Fermi level is almost perfectly pinned to the valence band edge of Ge at the metal=Ge interface for various element metals. 7,8) This fact suggests that the Fermi level pinning (FLP) on Ge may be limited by an intrinsic mechanism. Therefore, understanding the FLP mechanism and controlling the SBH on n-Ge are strongly required.Recently, FLP alleviation has been demonstrated in ultrathin-film [GeO 2 , 9) Al 2 O 3 , 9) GeN, 10) SiN,11) MgO,12) Si,13) ZnO, 14) TiO 2 , 15) W-encapsulating Si, 16) indium tin oxide (ITO) 17) ] insertion at the element metal=Ge interface. When the direct metal=Ge interface is replaced by the metal= ultrathin film and ultrathin film=Ge interfaces, the strong FLP at the direct metal=Ge interface becomes less significant. Nevertheless, since the interface layer resistance is added, the direct metal=Ge interface with a low SBH is more preferable from the viewpoint of contact resistance reduction. With respect to the direct metal=Ge interface, it has recently been reported that the SBHs at epitaxial Fe 3 Si, 18) α-TiGeN, 19) epitaxial Mn 5 Ge 3 , 20) epitaxial NiGe 2 , 21) graphene, 22) and Sn 23) =n-Ge interfaces are relatively low, which deviates from the trend of strong FLP. 7,8) Some of them 18,20,21,23) considered that the FLP on Ge might not be determined by an intrinsic but extrinsic origin. It is inferred that those two kinds of experimental results may include a key aspect to understand the FLP mechani...

show abstract

Alleviation of fermi-level pinning effect at metal/germanium interface by the insertion of graphene layers

Cited by 25 publications

References 18 publications

Contacts between Two- and Three-Dimensional Materials: Ohmic, Schottky, and p–n Heterojunctions

Contacts between Two- and Three-Dimensional Materials: Ohmic, Schottky, and p–n Heterojunctions

Passivation of Germanium by Graphene for Stable Graphene/Germanium Heterostructure Devices

Reexamination of Fermi level pinning for controlling Schottky barrier height at metal/Ge interface

Contact Info

Product

Resources

About