3 research outputs found
Graphene-Si CMOS oscillators
Graphene field-effect transistors (GFETs) offer a possibility of exploiting unique physical properties of graphene in realizing novel electronic circuits. However, graphene circuits often lack the voltage swing and switchability of Si complementary metal-oxide-semiconductor (CMOS) circuits, which are the main building block of modern electronics. Here we introduce graphene in Si CMOS circuits to exploit favorable electronic properties of both technologies and realize a new class of simple oscillators using only a GFET, Si CMOS D latch, and timing RC circuit. The operation of the two types of realized oscillators is based on the ambipolarity of graphene, i.e., the symmetry of the transfer curve of GFETs around the Dirac point. The ambipolarity of graphene also allowed to turn the oscillators into pulse-width modulators (with a duty cycle ratio ∼1 : 4) and voltage-controlled oscillators (with a frequency ratio ∼1 : 8) without any circuit modifications. The oscillation frequency was in the range from 4 kHz to 4 MHz and limited only by the external circuit connections, rather than components themselves. The demonstrated graphene-Si CMOS hybrid circuits pave the way to the more widespread adoption of graphene in electronics
Chiral transport of hot carriers in graphene in the quantum Hall regime
Photocurrent (PC) measurements can reveal the relaxation dynamics of
photo-excited hot carriers beyond the linear response of conventional transport
experiments, a regime important for carrier multiplication. In graphene subject
to a magnetic field, PC measurements are able to probe the existence of Landau
levels with different edge chiralities which is exclusive to relativistic
electron systems. Here, we report the accurate measurement of PC in graphene in
the quantum Hall regime. Prominent PC oscillations as a function of gate
voltage on samples' edges are observed. These oscillation amplitudes form an
envelope which depends on the strength of the magnetic field, as does the PCs'
power dependence and their saturation behavior. We explain these experimental
observations through a model using optical Bloch equations, incorporating
relaxations through acoustic-, optical- phonons and Coulomb interactions. The
simulated PC agrees with our experimental results, leading to a unified
understanding of the chiral PC in graphene at various magnetic field strengths,
and providing hints for the occurrence of a sizable carrier multiplication.Comment: 14 pages, 13 figure