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2 Dielectric Stacks for Electrostatically Actuated NEMS/MEMS Reliability
Published in James E. Morris, Krzysztof Iniewski, Nanoelectronic Device Applications Handbook, 2017
Gang Li, Ulrik Hanke, Xuyuan Chen
The experimental results suggest that the effects of both hole injection and electron injection should be taken into account when we analyze charge accumulation. To better understand the above-mentioned charge injection behavior, we have to investigate the charge transport mechanism in a general MIS capacitor structure under high bias voltage. In fact, charge transport in the insulator of an MIS capacitor structure under an electric field depends not only on the insulator itself but also on the interaction of the insulator with its contact electrodes [15,16]. Consequently, carrier conduction processes can be classified into two groups: (i) bulk-limited (Poole–Frenkel, ohmic, and space-charge-limited) conduction and (ii) electrode-limited (Schottky and Fowler–Nordheim) conduction [17].
Thin Film Transistors
Published in Juan Bisquert, The Physics of Solar Energy Conversion, 2020
In the first case, the organic film has properties similar to an inorganic semiconductor, with an established degree of doping and a well-developed band bending, as indicated in Figure 14.2 and in Figure 9.18. This behavior corresponds to a conventional inorganic transistor such as the metal-insulator-semiconductor field effect transistor (MISFET). In this model, the energy diagram is similar to a standard metal-insulator-semiconductor (MIS) capacitor (Sze, 1981), see Figure 9.20, although the TFT is a variable resistor from D to S. In the case of an n-type semiconductor material, a positive gate voltage produces an accumulation of electrons in the space charge region at the semiconductor–insulator contact, while a negative gate voltage produces depletion of electrons and further negative bias will lead to the appearance of holes at the contact by the formation of an inversion layer. A more detailed analysis must consider the electrostatics of the semiconductor space charge, depending on Vg (Yong et al., 2011). The three possible regimes of gate voltage in a standard p/type metal-oxide-semiconductor (MOS) transistor are shown in Figure 9.18. The accumulation of carriers near the interface and the depletion characteristics can be detected by capacitance techniques (Hyuk-Ryeol et al., 1998). The normal mode of operation of a conventional MISFET results from the formation of a minority-carrier channel in the strong inversion regime; see Figures 9.19 and 9.20. The threshold voltage required for the onset of current conduction in the channel is that at which the Fermi level at the insulator–semiconductor interface crosses the middle of the gap.
Thin Film Transistors
Published in Juan Bisquert, Nanostructured Energy Devices, 2017
In the first case, the organic film has properties similar to an inorganic semiconductor, with an established degree of doping and a well-developed band bending, as indicated in Figure 5.2 and in Figure ECK.9.18. This behavior corresponds to a conventional inorganic transistor such as the metal-insulator-semiconductor field-effect transistor (MISFET). In this model, the energy diagram is similar to a standard metal-insulator-semiconductor (MIS) capacitor (Sze, 1981), see Figure ECK.9.20, although the TFT is a variable resistor from D to S. In the case of an n-type semiconductor material, a positive gate voltage produces an accumulation of electrons in the space charge region at the semiconductor–insulator contact, while a negative gate voltage produces depletion of electrons and further negative bias will lead to the appearance of holes at the contact by the formation of an inversion layer. A more detailed analysis must consider the electrostatics of the semiconductor space charge, depending on Vg (Yong et al., 2011). The three possible regimes of gate voltage in a standard p/type metal-oxide-semiconductor (MOS) transistor are shown in Figure ECK.9.18. The accumulation of carriers near the interface and the depletion characteristics can be detected by capacitance techniques (Hyuk-Ryeol et al., 1998). The normal mode of operation of a conventional MISFET results from the formation of a minority-carrier channel in the strong inversion regime; see Figure ECK.9.19 and Figure ECK.9.20. The threshold voltage required for the onset of current conduction in the channel is that at which the Fermi level at the insulator–semiconductor interface crosses the middle of the gap.
Control of subthreshold swing using an in situ PEALD nano-laminated IGZO/Al2O3 multi-channel structured TFT
Published in Journal of Information Display, 2023
Won-Bum Lee, Yoon-Seo Kim, Jin-Seong Park
To verify what caused the different trend from previous reports based on the increase in active layer thickness, the vertical band alignment (B–B′) of the gate insulator and active layer was simulated under the operational state of VGS = 10 V and VDS = 0.1 V for the 1S, 3S, 5S, and 10S TFTs, as shown in Figure 4. In general, most of the applied electric field in the metal insulator semiconductor (MIS) capacitor is assigned to the insulator layer to form the capacitance. In the semiconductor layer, band bending occurs depending on the influence of the carrier concentration or thickness [20]. The band bending occurs primarily near the interface between the gate insulator and active layer, and the electric field is not applied to the entire semiconductor layer. Because semiconductors (IGZO) and insulators (Al2O3) are sequentially stacked, this may be different from applying an electric field to the normal MIS structure. When the gate bias (VGS) is applied, the role of Al2O3 in the multilayer of 2-nm-IGZO/3-nm-Al2O3 is to enhance the degree of band bending of IGZO. In the 1S, 3S, 5S, and 10S TFTs, the total band bending values of IGZO were 0.03, 0.06, 0.09, and 0.11 V, respectively, and the total voltage applied to Al2O3 was 0.00, 0.04, 0.04, and 0.41 V at the enlarged conduction band, as shown in Figure 4(a–d) and as listed in Table 2. Table 2 also lists the decompositions of applied potential on the G.I (SiO2), IGZO, and Al2O3 layers under the operational state. Accordingly, the band bending energy of the first front IGZO layer gradually increased to 0.03, 0.04, 0.04, and 0.05 eV in the 1S, 3S, 5S, and 10S TFTs, respectively. Therefore, the increase in mobility based on the increase in the number of stacks was primarily due to the enhancement of band bending of the first front IGZO layer by the multi-stacked Al2O3 layer.