Modeling of Organic Metal–Insulator– Semiconductor Capacitor

Investigation of the Intrinsic Nature of Organic Semiconductors Using a Metal Contact-Induced Capacitance Study in Organic Metal–Insulator–Semiconductor Capacitors

“…. To match the flat-band voltage ( V FB ), the fixed charge ( Q f ) at the semiconductor–insulator interface is adjusted as mentioned in the table . The C – V characteristics of P3HT-based TG-MISCAP and BG-MISCAP, as shown in Figure a,b, respectively, are in good agreement with the experimental curves.…”

“…This results in more charge concentration within the semiconductor ( Q s ), leading to the semiconductor capacitance ( C s = | dQ s / d ψ s |, where ψ s is the voltage drop across the semiconductor) being very high compared to C i to provide C = C i = C max . This is referred to as the case of strong accumulation . On the contrary, upon applying a positive gate voltage, the electric field within the semiconductor causes the space charge distribution to be away from the semiconductor–insulator interface (still keeping the concentration at the body contact unaltered), which essentially reduces the charge concentration within the semiconductor layer.…”

“…At a higher positive gate voltage, the semiconductor layer almost becomes an insulator, resulting in C s being equal to the geometrical capacitance, i.e., C s = ϵ s ·ϵ 0 / d s , where d s is the thickness of the semiconductor. This can be considered as weak accumulation, and the corresponding capacitance ( C min ) can be expressed as where ϵ i and d i are the permittivity and the thickness of the gate dielectric layer, respectively. Consequently, the ratio of C max and C min is written as In particular, for P3HT-based TG-MISCAP, ϵ i ,LiF ≈ 9, ϵ s,P3HT ≈ 3, d i ,LiF ≈ 350 nm, and d s,P3HT ≈ 140 nm yield C max / C min = 2.2 as compared to the experimental value of 2.3.…”

“…One explicit question is whether the pristine organic semiconductors are unintentionally doped or intrinsic. One school of thought strongly believes in the existence of involuntary doping of the organic semiconductor (or polymers) during synthesis or processing. − Another school of thought does not concur with the concept of involuntary doping; rather, it considers that the charge injection from the metal to the semiconductor through a Schottky barrier is the main source of charge within the semiconductor. , Metal–insulator–semiconductor (MIS) capacitors, which are known to be essential diagnostic devices for studying field-effect transistors, can be a model system to understand the metal–insulator interface or the metal–semiconductor interface by analyzing capacitance–voltage ( C – V ) characteristics. ,, The existence of doping is mainly claimed on the basis of the linear part of the ( C –2 – V GB ) curve using the Mott–Schottky relation which is obtained from the standard C – V relation of MIS capacitors where C is the capacitance per unit area of the MIS capacitor, C i is the capacitance per unit area of the gate insulator, ϵ 0 is the permittivity of the free space, ϵ s is the dielectric constant of the semiconductor, V GB is the applied voltage at the gate electrode, V FB is the flat-band voltage, and N a/d is the doping concentration of the semiconductor (“a” denotes the acceptor, and “d” the donor). ,− However, in the case of undoped organic semiconductors, adopting the Mott–Schottky equation has been considered to be erroneous, as reported recently. , A physics-based analytical model to obtain the charge concentration, surface potential, and capacitance of the organic MIS capacitor has been recently demonstrated by our group. , The drift-diffusion of the charge carriers that are injected through the Schottky contact at the metal–semiconductor interface appears to be responsible for the capacitance variation with respect to voltage. A similar trend has also been observed in organic diodes. ,, Nevertheless, the universality of contact-induced charge injection has not yet been validated experimentally.…”

The Potential Barrier and Thermal Stability Dependence on PI Thickness of Al/PI/c-Si Schottky Diode

“…In the recent time, semiconductors are present in most of the modern electronic devices, because of the foundation of the electronic systems that play a crucial role in technology [2]. Metal-organic insulator-semiconductor structures obtained remarkable interest, due to the fact that these devices serve as a cost-effective alternative to traditional common junctions on low grade polycrystalline silicon thin films [3][4][5].…”