The current–voltage and capacitance–voltage characteristics of molecularly modified β-carotene/n-type Si junction structure with fluorescein sodium salt

β-Carotene–FSS organic semiconductor/n-type Si structure has been characterized by current–voltage and capacitance–voltage methods. A deviation in I–V characteristic of the diode is observed due to effect of series resistance and interfacial layer. Cheung's functions were used to calculate diode parameters. The ideality factor, series resistance and barrier height values of the diode are n = 1.77, R_s = 10.32 (10.39) kΩ and 0.78 eV. The obtained ideality factor suggests that Au/β-carotene–FSS/n-Si Schottky diode has a metal–SiO₂ oxide layer plus organic layer–semiconductor (MIOS) configuration. The capacitance–voltage characterizations of Au/β-carotene–FSS/n-Si diode at different temperatures were performed. The capacitance of the diode changes with temperature. The barrier height and ideality factor obtained from C–V curves are 0.67 eV and 1.68. The interface density properties of the diode are analyzed and the shape of the density distribution of the interface states is in the range of E_c −0.49 to −0.62 eV. It is evaluated that the FSS organic layer controls electrical charge transport properties of Au/β-carotene/n-Si diode by excluding effects of the β-carotene and SiO₂ residual oxides on the hybrid diode.     

未退火Co/n-poly-SiGe肖特基接触不均匀性研究

在n型单晶硅衬底上,用射频磁控溅射法沉积Si1-x Gex薄膜,在850℃下对薄膜进行40min磷扩散,制备出n-poly-Si1-x Gex.俄歇电子谱(AES)测试表明,Si1-xGex薄膜的Ge含量约为18％,即磷扩散后得到n-poly-Si0.82 Ge0.18.随即在n-poly-Si0.82 Ge0.18薄...     

Electrical characteristics of an organic thin copolymer/p-Si Schottky barrier diode

We have fabricated a poly(aniline-3-methyl thiophene) organic thin material on p-Si substrate by placing a solution of copolymer in acetonitrile on top of a p-Si substrate and then evaporating the solvent. The electrical and interface state density properties of the poly(aniline-3-methyl thiophene) copolymer/p-Si/Al diode have been investigated through methods using current-voltage (I-V), Cheung's, and a modified Norde's function. Good agreement was observed with the values of barrier height as obtained from all of these methods. The diode shows a non-ideal I-V behavior with an ideality factor greater than unity, which could be ascribed to the interfacial layer, interface states and series resistance. The interface state density of diode was determined using the forward-bias I-V characteristic technique at room temperature, and it decreases exponentially with bias from 1.39 × 10¹⁶ cm⁻² eV⁻¹ in (0.06 − E_v) eV to 4.86 × 10¹⁵ cm⁻² eV⁻¹ in (0.51 − E_v) eV.     

8 MeV electron irradiation studies on electrical characteristics of Cu(In,Ga)Se2 solar cells

Cu(In,Ga)Se₂ (CIGS) solar cells are gaining considerable interest due to their high optical absorption coefficient and adjustable band gap, which enables them to achieve high conversion efficiency and also present many promising applications in space power systems. In this paper we report the results of the effect of temperature and 8 MeV electron irradiation on the electrical characteristics of ZnO/CdS/Cu(In,Ga)Se₂/Mo polycrystalline thin-film solar cells under forward and reverse bias studied in the temperature range 270-315 K. The solar cells were subjected to 8 MeV electron irradiation from the Microtron accelerator and were exposed to graded doses of electrons up to 75 kGy. I-V characteristics of the cells under dark and AM 1.5 illumination condition were studied before and after the irradiation. Capacitance measurements were also carried out at various frequencies before and after irradiation. In the measured temperature range, the dark current contribution is due to the generation-recombination of the minority carriers in the depletion region. The ideality factor is found to decrease with increase in temperature. It seems that electron irradiation has not altered the dark current conduction mechanism significantly. The effect of electron irradiation on the solar cell parameters such as fill factor (FF), conversion efficiency (η), saturation current (I_o), short circuit current (I_sc), open circuit voltage (V_oc), and ideality factor (n) was studied. They were found to be stable up to 75 kGy of electron dose as only small changes were observed in the solar cell parameters.     

DNA-based organic-on-inorganic devices: Barrier enhancement and temperature issues

Electrical measurements have been reported sandwich device fabricated from DNA molecular film located between Al and p-type InP inorganic semiconductor. We have observed that DNA-based this structure shows an excellent rectifying behavior, and that the DNA film increases the effective barrier height by influencing the space charge region of InP. We have also evaluated electrical characteristics of the DNA-based device in a wide temperature range.     

The interface states analysis of the MIS structure as a function of frequency

The energy distribution of interface states (N_ss) and their relaxation time (τ) were of the fabricated the Al/SiO₂/p-Si (MIS) structures were calculated using the forward bias current-voltage (I-V), capacitance-frequency (C-f) and conductance-frequency (G-f) measurements. Typical ln[I/(1 − exp(−qV/kT)] versus V characteristics of MIS structure under forward bias show one linear region. From this region, the slope and the intercept of this plot on the current axis allow to determine the ideality factor (n), the barrier height (Φ_b) and the saturation current (I_S) evaluated to 1.32, 0.77 eV and 3.05 × 10⁻⁹ A, respectively. The diode shows non-ideal I-V behaviour with ideality factor greater than unity. This behaviour is attributed to the interfacial insulator layer at metal-semiconductor interface, the interface states and barrier inhomogeneity of the device. The energy distribution of interface states (N_ss) and their relaxation time (τ) have been determined in the energy range from (0.37 − E_v) to (0.57 − E_v) eV. It has been seen that the N_ss has almost an exponential rise with bias from the mid gap toward the top of valance band. In contrary to the N_ss, the relaxation time (τ) shows a slow exponential rise with bias from the top of the E_v towards the mid gap energy of semiconductor. The values of N_ss and τ change from 6.91 × 10¹³ to 9.92 × 10¹³ eV⁻¹ cm⁻² and 6.31 × 10⁻⁴ to 0.63 × 10⁻⁴ s, respectively.     

Degradation pattern of contact resistance and characteristic trap energy in blue organic light-emitting diodes

Thin and lightweight organic light-emitting diodes (OLEDs) are promising candidates for next-generation rollable displays; they offer numerous advantages, such as scalable manufacturing, high color contrast ratio, flexibility, and wide viewing angle. Despite the numerous merits of OLEDs, the insufficient lifetime and stability of blue OLEDs remain unresolved, thereby necessitating a feedback strategy for lifetime extension. Herein, we propose a simple yet effective methodology to determine the contact resistance (R_CT) and characteristic trap energy (E_T) of OLEDs simultaneously in the trapped-charge-limited-conduction regime, where electroluminescence occurs primarily. To validate our approach, the extracted R_CT and E_T values are directly compared with each other by connecting a commercial resistor (R_C) to a blue OLED in series. The percent errors discovered in R_C and E_T are less than 7% and 4%, demonstrating the high feasibility and accuracy of our approach. We further employ this method to study the degradation mechanism of a blue OLED by presenting the electrical stress time- and cycle-dependent R_CT, E_T, ideality factor, and turn-on voltage, revealing different degradation patterns of the metal-to-transport layer interface and emission layer, respectively. Our results provide better insights into the electrical parameter extraction method and electrical current degradation mechanism in blue OLEDs.     

Current–voltage and capacitance–voltage characteristics of Al Schottky contacts to strained Si-on-insulator in the wide temperature range

The electrical characteristics of Al/strained Si-on-insulator (sSOI) Schottky diode have been investigated using current–voltage (I–V) and capacitance–voltage (C–V) measurements in the wide temperature range of 200–400 K in steps of 25 K. It was found that the barrier height (0.57–0.80 eV) calculated from the I–V characteristics increased and the ideality factor (1.97–1.28) decreased with increasing temperature. The barrier heights determined from the C–V measurements were higher than those extracted from the I–V measurements, associated with the formation of an inhomogeneous Schottky barrier at the interface. The series resistance estimated from the forward I–V characteristics using Cheung and Norde methods decreased with increasing temperature, implying its strong temperature dependence. The observed variation in barrier height and ideality factor could be attributed to the inhomogeneities in Schottky barrier, explained by assuming Gaussian distribution of barrier heights. The temperature-dependent I–V characteristics showed a double Gaussian distribution with mean barrier heights of 0.83 and 1.19 eV and standard deviations of 0.10 and 0.16 eV at 200–275 and 300–400 K, respectively. From the modified Richardson plot, the modified Richardson constant were calculated to be 21.8 and 29.4 A cm⁻² K⁻² at 200–275 and 300–400 K, respectively, which were comparable to the theoretical value for p-type sSOI (31.6 A cm⁻² K⁻²).     

Effects of illumination on capacitance characteristics of Au/3C-SiC/p-Si/Al diode

Au/3C-SiC/p-Si/Al Schottky barrier diode was prepared using atmospheric pressure chemical vapor deposition technique. The device parameters such as barrier height, ideality factor, and series resistance were calculated using current-voltage characteristics, and were found to be 0.44 eV, 1.55, and 1.02 × 10⁴ Ω, respectively. The photocapacitive properties of the diode were studied under various illumination intensities. The transient photocapacitance measurements indicate that the capacitance of the Au/3C-SiC/p-Si/Al Schottky diode is very sensitive to illumination. The photocapacitance of the diode increases with increase in illumination intensity. The increase in photocapacitance with increase in illumination intensity suggests that these devices could be utilized as a photocapacitive sensor for optical sensors.     

The analysis of lateral distribution of barrier height in identically prepared Co/n-Si Schottky diodes

We have studied the experimental linear relationship between ideality factors and barrier heights (BHs) for Co/n-Si metal–semiconductor (MS) structures with a doping density of about 10¹⁵ cm⁻³. The barrier heights for the Co/n-type Si metal–semiconductor structures from the current–voltage (I–V) characteristics varied from 0.64 to 0.70 eV, the ideality factor n varied from 1.18 to 1.26, and from reverse bias capacitance–voltage (C⁻²–V) characteristics the barrier height varied from 0.68 to 0.81 eV. The experimental barrier height distributions obtained from the I–V and C⁻²–V characteristics were fitted by a Gaussian distribution function, and their mean values were found to be 0.67 and 0.75 eV, respectively. Furthermore, the lateral homogeneous BH value of approximately 0.81 eV for Co/n-Si metal–semiconductor structures was obtained from the linear relationship between experimental effective BHs and ideality factors.