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A method to realize a novel hybrid orientations of Si surfaces, Si(111) on Si(110), has been developed by use of a Si(111)/3C-SiC(111)/Si(110) trilayer structure. This technology allows us to use the Si(111) portion for the n-type and the Si(110) portion for the p-type channels, providing a solution to the current drive imbalance between the two channels confronted in Si(100)-based complementary metal oxide semiconductor (CMOS) technology. The central idea is to use a rotated heteroepitaxy of 3C-SiC(111) on Si(110) substrate, which occurs when a 3C-SiC film is grown under certain growth conditions. Monomethylsilane (SiH 3 –CH 3 ) gas-source molecular beam epitaxy (GSMBE) is used for this 3C-SiC interlayer formation while disilane (Si 2 H 6 ) is used for the top Si(111) layer formation. Though the film quality of the Si epilayer leaves a lot of room for betterment, the present results may suffice to prove its potential as a new technology to be used in the next generation CMOS devices.

This paper reports preparation of top-gate epitaxial graphene FETs (EGFETs) on silicon substrates. Epitaxial graphene is obtained from a thermal decomposition at the surface of a 3C–SiC layer grown on Si substrates. We provide the first demonstration and comparison of the EGFETs fabricated on Si(1 1 0) and Si(1 1 1) substrates. For all EGFETs, an n-type transistor operation is observed by the gate voltage modulation. We find that the Si(1 1 1) substrates give better flatness at the surface of the 3C–SiC layer. As a result, the EGFETs fabricated on Si(1 1 1) substrates exhibit higher channel currents than those on Si(1 1 0) substrates.

We have fabricated and characterized the field effect transistors having an epitaxial-graphene channel grown on Si substrates. Epitaxial graphene is usually formed on SiC substrates by ultrahigh-vacuum (UHV) annealing. We used an approach to grow 3C–SiC layer on Si substrates and subsequently to anneal them in UHV to make few layers of graphene on the sample surface. Backgate transistors were able to be formed by using the SiC layer as a gate insulator. Although the gate-leakage current is not negligible, the drain current modulation by means of the gate voltage is confirmed by extracting the channel current from the total drain current. A new evaluation method of the area contact resistance between graphene and metal is also proposed.

By conducting a 1200°C vacuum annealing of a 3C-SiC(111) ultrathin film preformed on a Si(110) surface, we have succeeded in forming a graphene layer on a Si substrate. Raman-scattering spectrum from this surface presents a distinct 2D band, whose deconvolution into four subcomponents indicates that the film mostly consists of a two-layer graphene. The peak position is blue-shifted from that of a free-standing graphene formed by a mechanical exfoliation method, suggesting a compressive stress in the film. [DOI: 10.1380/ejssnt.2009.107]

In this work, the epitaxial graphene channel formed on 3C-SiC grown on a Si substrate backgate transistor was designed, fabricated and characterized for electronic and optoelectronic applications. Even though a significant amount of the gate leakage current is observed, the experimental results show the device works as an n-type transistor as well as an infrared photovoltaic transistor with the backgate modulation. The observation of the ambipolar behavior verifies the unique property of the graphene layers. The epitaxial graphene is believed to be unintentionally p-type with the Fermi level offset around +0.11∼+0.12 V at the Dirac point. The drain saturated current of the graphene channel transistors is on the order of mA/mm. The photo-generated current can be achieved up to almost 20nA, corresponding to 0.06 mA/W in photo-responsivity at 0.5-V drain-source bias voltage and 0.5-V gate voltage. The backgate voltage tuning spectral characteristic is also demonstrated. The graphene based transistors have a potential application in infrared detection.

We have fabricated and characterized the field effect transistors having epitaxial-graphene channel grown on Si substrates. Epitaxial graphene is usually formed on SiC substrates by ultrahigh-vacuum (UHV) annealing. We used an approach to grow 3C-SiC(111) on Si substrates and subsequently to anneal it in UHV to make few layers of graphene on the sample surface. Backgate transistors using the SiC layer as a gate insulator was characterized. Although significant gate leakage current is observed, the drain current modulation by the gate voltage is confirmed by extracting the channel current from the total drain current. The drain saturation current of the graphene-channel transistors is in the order of mA/mm due to the large contact resistance that should be minimized in future study.

In this research, ambipolar behavior, which is one of graphene's unique characteristics, is studied for the epitaxial graphene formed on 3C-SiC grown on a Si substrate. The graphene channel is believed to be unintentionally p-type-doped at Dirac-point voltages of approximately +0.11 to +0.12 V. However, as drain voltage negatively increases, Dirac point voltage shifts. The drain current in the p-channel mode of operation saturates at a lower level than that in the n-channel mode of operation. These behaviors are caused by asymmetric carrier transport throughout channel-substrate heterojunctions (i.e., graphene, thin n-type SiC layer, and p-type Si substrate) and source/drain Schottky metal contacts. The interface between the p-type Si substrate and n-type SiC has a significant effect on transport in graphene channels. The results may be helpful for understanding transport in the device and for suppressing ambipolar operation, leading to a unipolar FET operation.

We have fabricated and characterized field-effect transistors (FETs) with an epitaxial graphene channel on a SiC layer grown on a Si substrate. Epitaxial graphene can be formed on SiC substrates by thermal decomposition of its surface under an ultrahigh-vacuum (UHV) condition. To incorporate the thermal decomposition of SiC on Si substrates, we used an approach of growing a thin 3C-SiC(111) layer on Si substrates and subsequently annealing them in UHV to form graphene on the surface of the 3C-SiC layer. Backgate-field-effect transistors using the SiC layer as a gate insulator were characterized. Although a large amount of gate-leakage current is observed, the drain current modulation by backgate voltage is confirmed by extracting the channel current from the total drain current. The extracted channel current characteristics also suggest that the extracted effective mobility exceeds the universal mobility of bulk silicon under similar circumstances.