Gate Voltage Dependence Of Mobility Research Articles

Temperature- and gate voltage-dependent I–V modeling of GaN HEMTs based on ASM-HEMT

Abstract In this paper, a temperature and gate voltage dependent current-voltage (I-V) model for Gallium nitride (GaN) high electron mobility transistors (HEMTs) devices is studied. In order to help researchers and designers simulate devices in the absence of experimental data and improve parameter extraction efficiency, the temperature and gate voltage dependence of mobility are discussed and incorporated into the proposed model which is revised from the standard advanced SPICE model (ASM) for GaN HEMTs. The mobility variations with gate voltage from -2 V to 6 V and temperature from 10 K to 1000 K are analyzed. The simulation results of our model are compared with the standard ASM-HEMT model, and the output and transfer characteristics of the device from 270 K to 420 K are simulated. Thereby, our model may simulate various applications of GaN HEMTs at different gate voltages and temperatures in the early stages of design and research.

Compact Modeling of Organic Thin-Film Transistors with Solution Processed Octadecyl Substituted Tetrabenzotriazaporphyrin as an Active Layer

Using 70-nm-thick spin-coated film of newly synthesized octadecyl substituted copper tetrabenzotriazaporphyrin (10CuTBTAP) as an active layer on a highly doped silicon (110) gate electrode substrates, output characteristics and transfer characteristics of bottom-gate bottom-contact organic thin-film transistors have been measured at room temperature. A compact model for thin-film transistors has been employed as a part of circuit design tool to extract device parameters, such as the charge-carrier mobility ${\mu }$ , the threshold voltage $V_{T}$ , and the contact resistances. Parallel measurements and analysis were performed on similarly constructed devices with a copper phthalocyanine(10CuPc) analog. The results reveal that the 10CuPc layer is relatively more susceptible to trapping degradation near the gate region than a 10CuTBTAP layer, which is significant in order to achieve stability in these transistors. The application of the simple square law in the classical MOS model provides a quicker but approximate interpretation of the transistor performance without providing information on the gate-voltage dependence of mobility and the effects of the contact regions. In this paper, the analysis of the contact regions is found to be very important for determining the difference in the performance of two transistors.

Current–voltage characteristics in organic field-effect transistors. Effect of interface dipoles

The role of polar molecules present at dielectric/semiconductor interfaces of organic field-effect transistors (OFETs) has been assessed employing the electrostatic model put forward in a recently published paper (Sworakowski et al., 2014). The interface dipoles create dipolar traps in the surface region of the semiconductor, their depths decreasing with the distance from the interface. This feature results in appearance of mobility gradients in the direction perpendicular to the dielectric/semiconductor interface, manifesting themselves in modification of the shapes of current–voltage characteristics. The effect may account for differences in carrier mobilities determined from the same experimental data using methods scanning different ranges of channel thicknesses (e.g., transconductances vs. transfer characteristics), differences between turn-on voltages and threshold voltages, and gate voltage dependence of mobility.

On the MOSFET Threshold Voltage Extraction by Transconductance and Transconductance-to-Current Ratio Change Methods: Part I—Effect of Gate-Voltage-Dependent Mobility

This paper presents a study of the effect of the gate-voltage-dependent mobility on the threshold voltage extraction in long-channel MOSFETs by the transconductance change method and recently proposed transconductance-to-current ratio change method, using analytical modeling and experimental data obtained on advanced silicon-on-insulator (SOI) FinFETs and ultrathin-body SOI MOSFETs with ultrathin high- gate dielectrics. It is shown that, at vanishingly small drain voltage and constant mobility, both methods yield the same values, coinciding with the position of the maximum of the second derivative of the inversion carrier density in respect to the gate voltage. However, such is not the case anymore when considering gate-voltage dependence of mobility around threshold. Analytical expressions for the errors in the values obtained by both methods due to mobility variation around threshold are obtained. Based on analytical modeling and experimental data, it is demonstrated that, for the same mobility variation, the resulting error on the extraction caused by the gate-voltage-dependent mobility is much smaller for the transconductance-to-current ratio change method than for the transconductance change method.

Self-consistent calculation of electronic states in AlGaAs/GaAs/AlGaAs selectively doped double-heterojunction systems under electric fields

The electronic states in AlGaAs/GaAs/AlGaAs selectively doped double-heterojunction (SD-DH) systems or single-quantum-well systems have been calculated self-consistently for the case where an external gate voltage is applied perpendicularly to the surface. The transition from symmetrical to asymmetrical distributions of electrons by the external field is predicted. The calculated variations of electron concentration with the gate voltage are found to be in good agreement with the experiment. The shoulder structures observed in the gate voltage dependence of mobility have been successfully accounted for and ascribed to the onset of electron population in the upper subbands. This analysis is expected to provide powerful means to evaluate the performance of SD-DH field-effect transistors and to optimize their design.