Field-effect transistors threshold voltage

Nanocrystals are receiving significant attention for nano-electronics application for the development of future nonvolatile, high density and low power memory devices [1-3]. In nanocrystal complementary metal oxide semiconductor (CMOS) memories, an isolated semiconductor island of nanometer size is coupled to the channel of a MOS field effect transistor (MOSFET) so that the charge trapped in the island modulates the threshold voltage of the transistor (Fig. 1). 

The operation principle of these TFTs is identical to that of the metal-oxide-semiconductor field-effect transistor (MOSFET) [617,618]. When a positive voltage Vg Is applied to the gate, electrons are accumulated in the a-Si H. At small voltages these electrons will be localized in the deep states of the a-Si H. The conduction and valence bands at the SiN.v-a-Si H interface bend down, and the Fermi level shifts upward. Above a certain threshold voltage Vth a constant proportion of the electrons will be mobile, and the conductivity is increased linearly with Vg - Vih. As a result the transistor switches on. and a current flows from source to drain. The source-drain current /so can be expressed as [619]... 

The transistor performance is generally characterized by field-effect transistor (FET) mobility (j i), current on/off ratio (f n/f0ff), and threshold voltage (Vj)-... 

Rashid, and G. Schitter, Threshold voltage shift in organic field effect transistors by dipole monolayers on the gate insulator , Journal of Applied Physics 96, 6431 (2004). 

Fig. 2.19. (a) Scheme of a transparent field effect transistor based on ZnO [191]. The gate electrode consists of tin-doped indium oxide (ITO) and the gate dielectric is a multilayer of AECE/TiCE (ATO). (b) Output characteristics (drain-source current as a function of the drain-source voltage) for different gate voltages. The saturation current is about 530 rA at a gate bias of 40 V. From this output characteristics a threshold voltage of 19 V and a field-effect mobility of 27 cm2 V-1 s-1 were calculated [192]... 

For example, the localized electronic states within the HOMO-LUMO gap impair the performance of the field-effect transistors by increasing the field-effect threshold voltage and reducing the effective mobility of charge carriers [100]. The surface density of electronic defects in high-quality single-crystal OFETs can be less than 10 ° cm ° [38], which corresponds to interdefect distances of 0.1 jm. 

Horowitz, G. et al.. The concept of threshold voltage in organic field-effect transistors, Adv. Mater. 10, 923, 1998. 

In the standard metal-oxide semiconductor field-effect transistor (MOSFET) drain-current equations, is a proportionality factor that relates the drain current /p, to the gate and drain voltages and V[)s, respectively the threshold voltage V, the channel width W and length L and the gate dielectric capacitance per unit area Cox. The standard drain-current equation for an -channel device in the linear region of operation - V) is [4]... 

Annie Wang, loannis Kymissis, Vladimir Bulovic, and Akintunde 1. Akin-wande. Tunable threshold voltage and flatband voltage in pentacene field effect transistors. Applied Physics Letters, 89(ll) 112109-3, 2006. 

A. I. Wang. Threshold voltage in pentacene field effect transistors with parylene dielectric. PhD thesis, Massachusetts Institute of Technology, 2004. 

Device-Oriented Models The Polymer Field Effect Transistor (FET) Structure Contacts in OFETs Extracting Mobility and Threshold Voltage for OFETs Organic LEDs... 

Fig. 2 (a) Output and (b) transfer characteristics of a near-ideal organic field-effect transistor in hole accumulation, (c) Extraction of mobility and threshold voltage from the square root plot of the saturation current... 

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