Effect of ferroelectric substrate on carrier mobility in graphene field-effect transistors

Abstract

Effect of LiNbO3 ferroelectric substrate on the carrier mobility in top gated graphene field-effect transistors (G-FETs) is demonstrated. It is shown that, at the same residual concentration of the charge carriers, the mobility in the G-FETs on the LiNbO3 substrate is higher than that on the SiO2/Si substrate. The effect is associated with reduction of Coulomb scattering via screening the charged impurity field by the field induced in the ferroelectric substrate, but significant only for mobilities below 1000 cm2/V s. Raman spectra analysis and correlations established between mobility and microwave loss tangent of the Al2O3 gate dielectric indicate that the charged impurities are located predominantly at the gate dielectric and/or at the gate dielectric/graphene interface and are likely associated with oxygen vacancies.

Effect of oxide traps on channel transport characteristics in graphene field effect transistors

“…(9)] to the measured capacitance-gate voltage characteristic using Eqs. (10)- (14). The extracted interface state density is high, which is reasonable since the capacitance variation of about 3% is much smaller than expected from an intrinsic structure.…”

“…All charge is automatically taken into account by using Eq. (14). A change in the position of E F will change interface charge, Q it , and entail a change in Q G; and finally (dotted line).…”

“…Therefore, in our model, we assume that the work function difference between the gate metal and graphene can be neglected in Eq. (14). The relation between the applied gate voltage and Fermi level position according to Eq.…”

“…5,[7][8][9] The disadvantage of these methods is, that the conditions under which the mobility is obtained are not the same as for a transistor structure. Alternatively, a commonly accepted experimental method for finding mobility values by direct measurements on G-FETs is to fit a simplified expression for the drain resistance to drain resistance--gate voltage characteristics [10][11][12][13][14] R ¼ R c þ ðL=WÞðqlÞ À1 ððn 0 2 0 þ ðCðV g À V Dirac Þ=qÞ 2 Þ À1=2 :…”

Characterization of Al2O3 gate dielectric for graphene electronics on flexible substrates

“…The tan δ tot in the gate dielectric of GFETs is correlated to the carrier mobility in graphene. The carrier mobility increases sharply with the decrease of tan δ tot [15]. The measured tan δ tot , simulated tan δ s and tan δ ipl versus area of the inner electrode are shown in Fig.…”