Energy Density Distribution

description6 papers

group0 followers

lightbulbAbout this topic

Energy Density Distribution refers to the spatial arrangement of energy per unit volume or mass within a given system. It quantifies how energy is spread across different regions, influencing the system's behavior, stability, and interactions, particularly in fields such as physics, engineering, and environmental science.

lightbulbAbout this topic

The effect of PVA (Bi2O3-doped) interfacial layer and series resistance on electrical characteristics of Au/n-Si (110) Schottky barrier diodes (SBDs)

by Tuncay Tunç

2022, Current Applied Physics

Two types of Schottky Barrier Diodes (SBDs) with and without PVA (Bi 2 O 3-doped) polymeric interfacial layer, were fabricated and measured at room temperature in order to investigate the effects of the PVA (Bi 2 O 3-doped) interfacial... more

descriptionView Paper arrow_downwardDownload

The Investigation of Frequency and Voltage Dependence of Electrical Characteristics in Al/P3HT/p-Si (MPS) Structures

by Esra Yükseltürk

2022, Materials Today: Proceedings

Metal-polymer-semiconductor (Al/P3HT/p-Si) structures have been fabricated and their electrical characteristics have been investigated using capacitance-voltage (C-V) and conductance-voltage (G/-V) measurements. These measurements were... more

Fig. 1. Schematic diagram of the Al/P3HT/p-Si (MPS) structure and measurement system. SOE AE ee eS eee eee ee eee ees Eee The C-V and G/w-V measurements of the Al/P3HT/p-Si (MPS) structure was performed in the frequency range of 3 kHz-1 MHz by using HP 4192 A LF impedance analyzer (5 Hz-13 MHz) and the test signal of 50 mV,.). All measurements were carried out at room temperature, with the help of a microcomputer through an IEEE-488 ac/dc converter card in the cryostat to avoid from any external noise.

of R, of the Al/P3HT/p-Si (MPS) structure. The reverse bias C* vs V plots of Al/P3HT/p-Si (MPS) structure were drawn for intermediate and high frequencies (f=3 kHz) at room temperature to extract the real values of some main electrical parameters such as Vp, Na, Ep and ®,. Since the contribution of the surface states to excess capacitance and conductance can be ignored, the measured valued of them is quite low at high frequencies. The C’-V plots exhibit a straight line in a wide bias range, and diffusion potential has been found from the extrapolation of this line to the voltage axis (V=0). For the purpose of getting structure paremeter, the reverse bias C’-V plot was drawn and given in Fig.4. From the slope of this line, one can calculate the different parameters such as Vp, Na, Em, Ep and ®g [36-40]. The found parameters could be seen in Table 1. As shown in Table 1, the obtained Vp, ®g Ep values increase with the increasing frequencies. It has been observed that the voltage axis extrapolation have changed from the reverse bias to forward bias by increasing frequency. For a MS, MIS and MPS type structure, the relationship between C and V in the depletion layer capacitance can be expressed as [31];

Fig. 3. G/w-V plots of the Al/P3HT/p-Si (MPS) structure in the frequency range of 3 kHz-1 MHz. Fig. 2. C-V plots of the Al/P3HT/p-Si (MPS) structure in the frequency range of 3 kHz-1 MHz.

Fig. 5. D,- In(f) plot of Al/P3HT/p-Si (MPS) structure in the frequency range of 3 kHz-1 MHz. Fig. 4. C*-V plots of Al/P3HT/p-Si (MPS) structure in the frequency range of 3 kHz-1 MHz. where Ny is the effective density of states in Si valance band, the effective mass of holes m*;,= 0.55mo [32] and m, is the rest mass of the electron. As to the changes in the Op it was given in Fig.5. As it is seen, the frequency dependent value of BH (®g(C—V)) increases with increasing frequency. This expected behavior of ® ,(C-V) is attributed to particular density distribution of N,, and the interfacial layer [33, 35]. At the same time, the decrease in C with increasing frequency depends not only on the decrease in N,, but also on the increase in Wp. As can be noted in Table | the values of Vp. Na, Ep, ®g(C-V) and Wp for the MPS capacitor increase with increasing frequency, whereas the value of Na decreases due to the surface states and relaxation time.

Fig. 7. G/w-f graphs of Al/P3HT/p-Si (MPS) structure for various voltages in the frequency range of 3 kHz-1 MHz. Fig. 6. C-f graphs of Al/P3HT/p-Si (MPS) structure for various voltages in the frequency range of 3 kHz-1 MHz. When the C-V and G/w-V plots are obtained at sufficiently high frequency (f =1 MHz), the effect of surface states can be eliminated, since they do not follow ac signal above this frequency as mentioned before. In this case, the R, seems the most important parameter which causes the electrical characteristics of Schottky type structures to be non-ideal. To obtain the real capacitance and conductance, their values for high frequencies under forward and reverse bias were corrected as (C, and G,/a), for the effect of R, using the equations 7-9 [32].

Fig. 8 (a) The corrected C-V and (b) the corrected G/w-V plots of the Al/P3HT/p-Si (MPS) structure for 1 MHz and room temperature. where G, is the corrected conductance. As can be seen in Fig. 8(a), the values of corrected capacitance, C,, increase compared to the measured value o capacitance for 1 MHz especially in the depletion and accumulation regions. On the other hand, the values o corrected conductance, G,/@ decrease compared to providing that the charge transfer can take place through that be affected by R,, particularly at higher frequencies, structures and in the techniques used in measurements. inter polarization mechanism. Also, it can be attributed to traps localized at M/S interface. However, we observed cons ant at high voltages. he value of measured conductance as seen in Fig. 8(b), it is he interface. From the measured data, we also observed he values of corrected capacitance change with frequency. It is clear that both the C and G/o measurements can herefore a care should be exercised both in the preparation o This change in C, means that the dielectric constant of facial layer at M/S interfaces, whether native or deposited, changes with measured frequency because of the he trap charges which have enough energy to escape from the hat the values of corrected conductance remain almos

Fig. 10. Nss-In(f) plots of the Al/P3HT/p-Si (MPS) structure in the wide frequency range of 3 kHz-1 MHz. Fig. 9. R,-V plots of the Al/P3HT/p-Si MPS type structure in the frequency range of 3 kHz-1 MHz. region correspond to R, values. As can be seen in Fig. 9, the change in R, becomes rather important in the depletion and accumulation regions, but nearly independent of the frequency in the strong inversion and depletion regions. This variation of R, with the frequency can be attributed to the the existence of N,, at P3HT/p-Si interface, interfacial layer, surface and dipole polarization. We believe that the traped charges at surface states or interface traps can easily follow the external ac signal especially at low frequencies. In general, the source of R, could be due to the non-ohmic back contact, leakage paths at interfacial layer/back contact interface, the contact made by the probe wire to the gate, the resistance of the bulk semiconductor, an extremely non-homogeneity of doping concentrations atoms distribution in the semiconductor and interfacial layer. The C-V measurements of the MS, MIS and MPS type structures confirmed the effect of the R,, N,, and interfacial layer which can be considered as a layer structures with nonlinear resistance, N,, and capacitance. Also, it is well known that the density of N,, is a useful guide for the quality of semiconductor devices such as SBDs. There are several methods to determine N,, [17, 22]. Among them, Hill-Coleman method [41] is important in terms of being fast and reliable. According to this method, the density of surface states can be expressed as

descriptionView Paper arrow_downwardDownload

Analysis of electrical equivalent circuit of metal–insulator–semiconductor structure based on admittance measurements

by S. Kochowski

2022

An electrical equivalent circuit of Al–(thermal)SiO2–(n)Si structure has been proposed and the results of analysis of circuit parameters have been compared with classical methods of investigations of metal–insulator– semiconductor (MIS)... more

Fig. 1. Experimental C—U, (a) and G—U, (b) characteristics of Al-(thermal)SiO,—(n)Si structure recorded at f= 1 MHz. The MIS structure was kept at 300 K. The inset shows the plot v, vs. bias U, constructed by comparing experimental high frequency C—U, characteristic with calculated theoretical C—y, curve [10]. The MIS capacitance Coy as a C-U, maximum was determined from the characteristics, Se Thawed’: Lea<rel «x weiner ndind cane, hence tre: TORT ned nmettinl eaciciinene Diecessnilentiad weeseire Lewes cc: Skee TCT

Fig. 2. Capacitance C and normalized conductance Ga vs. frequency of Al-(thermal)SiO,—(n)Si structures at various biases (f= @/2m). The sample kept at 300 K. Symbols represent experimental data while full lines are the best fits of experimental data using the circuits from Fig. 3. In Fig. b) one can see characteristic maxima of normalized conductance corresponding to frequency dispersion of capacitance in Fig. a) (biases from —4 V to —2.5 V)

Fig. 3. Electrical equivalent circuits of the MIS structure for various bias ranges: a) U,<-5 V,b)-5 VS U, <-3 V, c) Ug >-3 V, Coy— insulator capacitance, Rs — serial resistance, L — circuit inductance, Csc — bias-dependent space charge layer capacitance, Cp — additional bias-dependent capacitance, CPE, » — constant phase elements characterized by Qj, and nj» parameters, R, — resistances voltage, occur and the capacitance dispersion exists in the frequency range wher<« these maxima are observed. We managed to describe the determined characteristics by equivalent circuits presented in Fig.3. These circuits contain: insulator capacitance Cox, serial resistance Rs, circuit inductance L, bias-dependent space charge layer ca- pacitance Csc, additional bias-dependent capacitance Cp, two constant phase elements CPE\» characterized by Q,2 and 2 parameters, and resistors R12. The electrica equivalent circuit of the MIS structure simplifies for bias range U,<-—5 V (toward: structure inversion, Fig. 3a) and U, >-—3 V (towards structure accumulation, Fig. 3c’ while for -5 VS U,<-3 V (structure depletion) the circuit contains all elements (Fig. 3b).

Fig. 4. Values of equivalent circuit parameters from Fig. 3 obtained at various biases U, (symbols): a) Coy— insulator capacitance, Csc — bias-dependent space charge layer capacitance, Cp — additional bias-dependent capacitance; b) R,; and R, resistances, Ry serial resistance; c) constant phase element parameters QO, Qoand parallel resistance R,= Q, '; d) constant phase elements parameters n, and n. Dashed line in (a) represents constant insulator capacitance Coy obtained from C—U, characteristics. Full line in a) shows a theoretical curve of space charge layer capacitance Cyc vs. bias calculated according to Ovsyuk formulas [9] where the surface potential v, was assigned to U, using inset in Fig. la. Dotted line in b) represents constant serial resistance R, obtained from G—V characteristics according to [8] —voltage characteristic. The estimated space charge layer capacitance Csc coincides with theoretical Csc curve calculated based on the u, value determined from C—U, characteristics for biases corresponding to inversion and depletion region of MIS structure (Fig. 4a). The essential features of the admittance characteristics of the MIS structures are described by the constant phase elements CPE; and CPE, connected in series with resistors R, and R2, respectively.

The presented results show that the proposed equivalent circuits with constant phase elements allow one to describe complex processes evoked by localized electron states in the MIS structures, pointing to the usability of the impedance spectroscopy method for the analysis of other materials and systems, especially where standard methods are difficult or impossible to apply. Tro. from measured normalized conductance in depletion. These time constants char- acterize exchange of electrons between SiO,—Si interface and semiconductor states. The tye_ values, presented in Fig. 5, are in very good agreement with 7 values. This suggests that time constants 7 and tyc_ are connected with the same electron process. Thus the constant phase element CPE) in series with R resistance describes the dis- persion phenomena evoked by the semiconductor-—insulator interface states. The time constant 7, is practically gate voltage independent. This kind of behaviour points to the presence of the deep traps in the semiconductor space charge region. The CPE, ele- ment with the parameter n, = 0.95 for U,<—5 V (v, <—13, see Fig.1) has “capacitive” character (for pure capacitance n = 1) and together with R, resistance they characterize he time constant of monoenergetic electron traps in a lower part of the energy gap of he semiconductor. For U,>-—3 V (v,>0), what corresponds to the traps located in an upper part of the energy gap; the CPE, element with the parameter n, = 0.46 con- nected with R, resistance describes electron processes with a broad spectrum of time constants.

descriptionView Paper arrow_downwardDownload

The effect of PVA (Bi2O3-doped) interfacial layer and series resistance on electrical characteristics of Au/n-Si (110) Schottky barrier diodes (SBDs)

by Tuncay Tunç

2021

Two types of Schottky Barrier Diodes (SBDs) with and without PVA (Bi2O3-doped) polymeric interfacial layer, were fabricated and measured at room temperature in order to investigate the effects of the PVA (Bi2O3-doped) interfacial layer on... more

descriptionView Paper arrow_downwardDownload

The effect of PVA (Bi2O3-doped) interfacial layer and series resistance on electrical characteristics of Au/n-Si (110) Schottky barrier diodes (SBDs)

by Tuncay Tunç

2021

Two types of Schottky Barrier Diodes (SBDs) with and without PVA (Bi2O3-doped) polymeric interfacial layer, were fabricated and measured at room temperature in order to investigate the effects of the PVA (Bi2O3-doped) interfacial layer on... more

descriptionView Paper arrow_downwardDownload

Energy density distribution profiles of surface states, relaxation time and capture cross-section in Au/n-type 4H-SiC SBDs by using admittance spectroscopy method

by AHMET KAYA

2016

Au/n-type 4H-SiC diodes were fabricated and their electrical characteristics have been investigated by using the capacitance/conductance-voltage-frequency (C–V –f and G/w − V –f) measurements method at room temperature. The main... more

descriptionView Paper arrow_downwardDownload

The effect of PVA (Bi2O3-doped) interfacial layer and series resistance on electrical characteristics of Au/n-Si (110) Schottky barrier diodes (SBDs)

by Prof.Dr. İbrahim USLU

2011

Two types of Schottky Barrier Diodes (SBDs) with and without PVA (Bi2O3-doped) polymeric interfacial layer, were fabricated and measured at room temperature in order to investigate the effects of the PVA (Bi2O3-doped) interfacial layer on... more

descriptionView Paper arrow_downwardDownload