Charge Carrier Mobility In Semiconductors Research Articles

Improved Determination of the Mobility and Built-In Voltage in Asymmetric Single-Carrier Devices

The steady-state charge-carrier mobility in semiconductors can be extracted from the space-charge-limited current in single-carrier devices. However, in many cases, a built-in voltage is present, which should be known accurately to obtain the correct mobility. Here, it is demonstrated that band bending at the injecting electrode has important consequences for the built-in voltage and the analytical description of the current-voltage characteristics. It is shown that the built-in voltage can be accurately determined from the slope of the current-voltage characteristics on a semilogarithmic scale. Knowing the effect of band bending on the injected current, a simple analytical equation for the drift-diffusion space-charge-limited current above the built-in voltage is derived, which allows for improved determination of the charge-carrier mobility from experimental data.

Critical Evaluation of Organic Thin-Film Transistor Models

The thin-film transistor (TFT) is a popular tool for determining the charge-carrier mobility in semiconductors, as the mobility (and other transistor parameters, such as the contact resistances) can be conveniently extracted from its measured current-voltage characteristics. However, the accuracy of the extracted parameters is quite limited, because their values depend on the extraction technique and on the validity of the underlying transistor model. We propose here a new approach for validating to what extent a chosen transistor model is able to predict correctly the transistor operation. In the two-step fitting approach we have developed, we analyze the measured current-voltage characteristics of a series of TFTs with different channel lengths. In the first step, the transistor parameters are extracted from each individual transistor by fitting the output and transfer characteristics to the transistor model. In the second step, we check whether the channel-length dependence of the extracted parameters is consistent with the underlying model. We present results obtained from organic TFTs fabricated in two different laboratories using two different device architectures, three different organic semiconductors and five different materials combinations for the source and drain contacts. For each set of TFTs, our approach reveals that the state-of-the-art transistor models fail to reproduce correctly the channel-length-dependence of the transistor parameters. Our approach suggests that conventional transistor models require improvements in terms of the charge-carrier-density dependence of the mobility and/or in terms of the consideration of uncompensated charges in the carrier-accumulation channel.

An alternative method for measurement of charge carrier mobility in semiconductors using photocurrent transient response

We report here a simple alternative method for measuring charge carrier drift mobilities in semiconductor devices. A typical falling photocurrent transient formula for switch-off-state was adjusted to obtain simultaneously electron and hole mobilities. For both undoped ZnO film and InAlAs/InGaAs quantum well structure, electron mobilities extracted from our model were compared with those obtained from maximum-entropy mobility-spectrum analysis method (ME-MSA). Our results demonstrated that electron mobility obtained from our photocurrent response model could serve as substitutes for a representative mobility obtained from ME-MSA.

Measuring the lateral charge-carrier mobility in metal-insulator-semiconductor capacitors via Kelvin-probe.

We report a Kelvin-probe method to investigate the lateral charge-transport properties of semiconductors, most notably the charge-carrier mobility. The method is based on successive charging and discharging of a pre-biased metal-insulator-semiconductor stack by an alternating voltage applied to one edge of a laterally confined semiconductor layer. The charge carriers spreading along the insulator-semiconductor interface are directly measured by a Kelvin-probe, following the time evolution of the surface potential. A model is presented, describing the device response for arbitrary applied biases allowing the extraction of the lateral charge-carrier mobility from experimentally measured surface potentials. The method is tested using the organic semiconductor poly(3-hexylthiophene), and the extracted mobilities are validated through current voltage measurements on respective field-effect transistors. Our widely applicable approach enables robust measurements of the lateral charge-carrier mobility in semiconductors with weak impact from the utilized contact materials.

Features of Printing and Display

The manufacture of display device is a complex technology. To reach the flexible display like E-paper, many manufacture process such as driving electrode circuit and transistor must be combined with printing technology. From the information reported, the application of gravure prints technology in organic electronics; off-set printing in EMI film and screen technology in circuit are summarized. The study was more about ink jet print technology. It was described that ink jet was used in OLED (Organic light-emitting diode), OTFT (organic thin film transistor), polymer solar cell/ Flexible organic photovoltaic cell and so on. An OE-A (organic electronics application) roadmap for the charge carrier mobility of semiconductors for organic electronics applications was given. To achieve the printed circuit, the nano silver conductive ink was applied and the ink jet circuit surface was tested by microscopy, the conductive and flexible silver film was with many advantages than screen circuit. It was concluded that the printing electronic will play important roll in the display development.

Possibility of contactless measurement of free charge carrier mobility in semiconductors by the uhf resonator method

A contactless method for measuring free charge carrier mobility in semiconductors using a uhf resonator is described. The method is based on the dependence of the Q of a quasistatic uhf resonator containing the semiconductor specimen on external magnetic field induction. Simple relationships are obtained which allow low determination of the magnetoresistive mobility from the change in Q of the external portion of the resonator under the action of a weak magnetic field.

Impurity diffusion and flicker fluctuations in charge-carrier mobility in semiconductors

The authors consider fluctuations in charge-carrier mobility due to diffusion of contaminating impurities and defects within a semiconductor volume. It is shown that this mechanism can lead to flicker fluctuations in charge-carrier concentration. It becomes possible to interpret the empirical Hooge-Kleinpenning-Vandamme relationship and certain other well known experimental data on the basis of the analysis performed.