Electrical Characteristics Of Diodes Research Articles

Excellent electroluminescence and electrical characteristics from p-CuO/i-Ga2O3/n-GaN light-emitting diode prepared by magnetron sputtering

With the development of semiconductor technology, ultraviolet light-emitting diodes (UV-LEDs) had been widely used in lighting, sterilisation, biological medical and other fields, which had broad market application prospects. The p-CuO/i-Ga2O3/n-GaN heterojunction diode was fabricated by radio frequency (RF) magnetron sputtering technology. The influence of ambient temperature on the electrical characteristics of diodes was studied, which exhibited typical diode rectification characteristics with high rectification ratios at different ambient temperatures. It was found that the temperature sensitivity of the forward current was greater than that of the reverse current when the driving voltage were ±3 V. Moreover, two luminescence peaks could be detected by the electroluminescence (EL) measurement, one was a strong ultraviolet (UV) luminescence peak at ∼370 nm, and the other was a wide deep-level luminescence peak at ∼500 nm. Eventually, the luminescence mechanism was discussed from the aspect of the energy band diagram of the heterojunction diode.

A Novel Simulation Method for Analyzing Diode Electrical Characteristics Based on Neural Networks

Based on the equivalent circuit model and physical model, a new method for analyzing diode electrical characteristics based on a neural network model is proposed in this paper. Although the equivalent circuit model is widely used, it cannot effectively reflect the working state of diode circuits under the conditions of large injection and high frequency. The analysis method based on physical models developed in recent years can effectively resolve the above shortcomings, but it faces the problem of a low simulation efficiency. Therefore, the physical model method based on neural network acceleration is used to improve the traditional, equivalent circuit model. The results obtained from the equivalent circuit model and the physical model are analyzed using the finite-difference time-domain method. The diode model based on a neural network is fitted with training data obtained from the results of the physical model, then it is summarized into a voltage–current equation and used to improve the traditional, equivalent circuit method. In this way, the improved equivalent circuit method can be used to analyze the working state of a diode circuit under large injection and high frequency conditions. The effectiveness of the proposed model is verified by some examples.

The electrical characteristics of ITO/CZTS/ZnO/Al and ITO/ZnO/CZTS/Al heterojunction diodes

In this study, ITO/a-CZTS/ZnO1/Al, ITO/ZnO2/a-CZTS/Al and ITO/ZnO2/c-CZTS/Al diode structures were produced by PLD technique and analysed, as well as data are presented. a-CZTS and ZnO thin films were grown as layer by layer thin films on ITO coated glass at room temperature and annealing process was not carried out for these samples. Morphologies and crystal structures of ZnO and a-CZTS thin films were analysed. ZnO thin films have been produced depending on an oxygen ambient gas pressure and a-CZTS thin film has been produced using low laser energies. While ZnO thin films exhibit crystal structure, a-CZTS has amorphous structure. In addition, c-CZTS thin film has also been annealed at 375 °C sulfurization temperature at which crystalline structure was obtained. Optical features of thin films were determined by UV–vis spectra and it was observed that a-CZTS and c-CZTS thin films have a high band gap and an ideal band gap, respectively. Diode structure of ITO/a-CZTS/ZnO1/Al has shown normal diode characteristics in dark environment and has different ideality factors for three regions in semi-logarithmic forward bias region. ITO/ZnO2/a-CZTS/Al diode structure has also shown a negative differential resistance and behaved like a tunnelling diode in dark environment exhibiting photoelectric effect under illuminated environment. Short circuit current density is very low, fill factor and open circuit voltage are quite high. In addition, ITO/ZnO2/c-CZTS/Al diode structure has shown some photo-electricity property under illumination conditions. The diode’s short circuit current density was found to be higher and open circuit voltage was very low. Electrical characteristics of diodes have been described in some details in this work.

Efficient, Nonintrusive Outcoupling in Organic Light Emitting Devices Using Embedded Microlens Arrays

We demonstrate efficient light extraction from the active region of bottom-emitting organic light emitting devices (OLEDs) using a high refractive index, nondiffractive hemispherical microlens array located between the transparent anode and embedded in the low refractive index glass substrate (n = 1.5). The subelectrode microlens array (SEMLA) results in a maximum external quantum efficiency of 70 ± 4% for green phosphorescent OLEDs (PHOLEDs). Furthermore, the wavelength- and viewing-angle-independent light extraction structure results in white PHOLED external efficiencies of 50 ± 3%. The SEMLA light extraction structure is nonintrusive; that is, it lies completely outside of the OLED structure. Since this design has no effect on the image resolution, it is compatible with applications for both displays and white light illumination, with no dependence on molecular transition dipole orientation and the active organic layers (and hence diode electrical characteristics) used in the PHOLED. Finally, due to th...

Significant improvement in the electrical characteristics of Schottky barrier diodes on molecularly modified Gallium Nitride surfaces

III-Nitride semiconductors face the issue of localized surface states, which causes fermi level pinning and large leakage current at the metal semiconductor interface, thereby degrading the device performance. In this work, we have demonstrated the use of a Self-Assembled Monolayer (SAM) of organic molecules to improve the electrical characteristics of Schottky barrier diodes (SBDs) on n-type Gallium Nitride (n-GaN) epitaxial films. The electrical characteristics of diodes were improved by adsorption of SAM of hydroxyl-phenyl metallated porphyrin organic molecules (Zn-TPPOH) onto the surface of n-GaN. SAM-semiconductor bonding via native oxide on the n-GaN surface was confirmed using X-ray photoelectron spectroscopy measurements. Surface morphology and surface electronic properties were characterized using atomic force microscopy and Kelvin probe force microscopy. Current-voltage characteristics of different metal (Cu, Ni) SBDs on bare n-GaN were compared with those of Cu/Zn-TPPOH/n-GaN and Ni/Zn-TPPOH/n-GaN SBDs. It was found that due to the molecular monolayer, the surface potential of n-GaN was decreased by ∼350 mV. This caused an increase in the Schottky barrier height of Cu and Ni SBDs from 1.13 eV to 1.38 eV and 1.07 eV to 1.22 eV, respectively. In addition to this, the reverse bias leakage current was reduced by 3–4 orders of magnitude for both Cu and Ni SBDs. Such a significant improvement in the electrical performance of the diodes can be very useful for better device functioning.

Observation of enhanced infrared absorption in silicon supersaturated with gold by pulsed laser melting of nanometer-thick gold films

We demonstrate that pulsed laser melting (PLM) of thin 1, 5, and 10 nm-thick vapor-deposited gold layers on silicon enhances its room-temperature sub-band gap infrared absorption, as in the case of ion-implanted and PLM-treated silicon. The former approach offers reduced fabrication complexity and avoids implantation-induced lattice damage compared to ion implantation and pulsed laser melting, while exhibiting comparable optical absorptance. We additionally observed strong broadband absorptance enhancement in PLM samples made using 5- and 10-nm-thick gold layers. Raman spectroscopy and Rutherford backscattering analysis indicate that such an enhancement could be explained by absorption by a metastable, disordered and gold-rich surface layer. The sheet resistance and the diode electrical characteristics further elucidate the role of gold-supersaturation in silicon, revealing the promise for future silicon-based infrared device applications.

The Effect of He-Ne and Diode Lasers on the Electrical Characteristics of Silicon Diode

The effect of He-Ne (632.8 nm) and diode (650 nm) lasers on the electrical characteristics of silicon diode have been studied. The electrical characteristics of the diode were recorded before laser irradiations, then the diode is subjected to He-Ne laser for 5 and 10 minutes and then the diode electrical characteristics were recorded for each time of exposure and the same was done in the case of irradiation with diode laser. The electrical characteristics of the diode before and after laser irradiations were compared and thermal effect was noticed when compared the effect of lasers irradiation and the well known temperature effect on the electrical characteristics of the diode. It was found that the effect of the He-Ne (632.8 nm) and diode laser (650 nm) on the electrical characteristics of silicon diode at exposure time of 5 minutes were comparable but for 10 minutes of exposure the effect of He-Ne laser irradiation on the characteristics was different from that of diode laser and this is due to the fact that the two lasers has different properties.

The stability of electrical characteristics of Ti/n-Si/Ag, Ti/n-Si/Cu and Ti/n-Si/AgCu diodes prepared under the same conditions with respect to increasing aging time

The purpose of this study is to fabricate Ti/n-Si/Ag, Ti/n-Si/Cu and Ti/n-Si/AgCu Schottky type diodes and to investigate the effects of aging time on the diode parameters such as ideality factor, barrier height, series resistance, interface state density and rectification ratio. High purity titanium (Ti) metal was deposited on the back side of the n-Si semiconductor and then the Ti/n-Si junction was annealed at 420°C in nitrogen atmosphere. This junction showed ohmic behavior. To fabricate rectifier contacts, Ag, Cu metals and AgCu alloy have been evaporated on the other polished surface of n-Si with Ti ohmic contact. Ag and Cu ratios in the AgCu alloy which are used in the process of preparing the Schottky contact were taken in equal weights. Thus, Ti/n-Si/Ag, Ti/n-Si/Cu and Ti/n-Si/AgCu Schottky type diodes were prepared under the same conditions. The current-voltage (I-V) characterization of Ti/n-Si/Ag, Ti/n-Si/Cu and Ti/n-Si/AgCu diodes were immediately made at room temperature in dark conditions. To investigate the effect of aging time, the I-V measurements of the diodes have been repeated after 1, 7, 15, 30 and 90 days. Characteristic parameters of the diode were calculated from the I-V measurements which are taken with respect to aging time. The results were compared. From these results, it can clearly be seen that the electrical characteristics of diode which is made from AgCu alloy are more stable than other two diodes.

Influence of illumination intensity and temperature on the electrical characteristics of an Al/p-GaAs/In structure prepared by thermal evaporation

The temperature and illumination intensity dependence of current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the Al/p-GaAs barrier diode were investigated. The ideality factor (n) and zero-bias barrier height (@Fb0) were found to be strongly temperature dependent and while @Fb0 is decreased, n is increased with decreasing temperature and illumination. The reverse biased I-V measurements under various illuminations exhibited a high photosensitivity. The values of Rs obtained from Cheung's method are decreased with increasing illumination intensity. The interface capacitance of the diode is increased with the increase of illumination intensities. The profiles of interface state density (Nss) distribution as a function of (Ess-Ev) were extracted from the forward I-V measurements by taking into account the bias dependence of the effective barrier heights (@fe) for device under dark, illumination and temperature conditions. Furthermore, modified Richardson plot has a good linearity over the investigated temperature range. As a result, the electrical characteristics of diode are affected not only in illumination but also in temperature. It is evaluated that the prepared diode can be used as photocapacitance sensor in modern electronic and optoelectronic devices.

Improving Forward Current Characteristics of Diode by X-Ray Irradiation

These papers investigates the effect of X-ray on forward current characteristics of diode. The forward current of diode after X-ray irradiation energy 40 keV at the exposure time ranging 5, 10 second was increased, while 15 and 20 second was decreased. X-ray causes changing of the electrical characteristics of diode. Series resistance is the main factor for analyze on forward current characteristics. From the results, X-ray can improve performance of diode at the exposure time for 5 and 10 second.

An experimental investigation of P–N diode electrical characteristics by soft X-ray annealing method

We present new experimental results for the electrical behaviors of P–N junction diodes irradiated by X-rays. The current–voltage ( I–V) characteristics of the P–N junction diodes were measured at room temperature. The reverse and forward current before and after irradiation can be explained relative to the following parameters: carrier generation lifetime ( τ g ), ideality factor ( n), series resistance ( R s ), and sheet resistance ( ρ). After irradiation at 40 and 55 keV, a small increment in the diode leakage current was seen, while at 70 keV of exposure, the leakage current was slightly decreased. On the other hand, the forward current was dramatically increased by about three orders of magnitude. In addition, the series resistance of the diodes was confirmed to be positively modified by the use of the soft X-ray annealing method.

High quality single-crystal germanium-on-insulator on bulk Si substrates based on multistep lateral over-growth with hydrogen annealing

Germanium-on-insulator (GOI) is desired for high performance metal-oxide-semiconductor transistors and monolithically integrated optoelectronics. We demonstrate a promising approach to achieve single-crystal defect-free GOI by using lateral over-growth through SiO2 window. The dislocations due to the lattice mismatch are effectively terminated and reduced in SiO2 trench by selective area heteroepitaxy combined with hydrogen annealing. Low defect density of 4×106 cm−2 and low surface roughness of 0.7 nm (root-mean-square) on GOI are confirmed by plan-view transmission electron microscopy and atomic force microscopy analysis. In addition, the excellent metal-semiconductor-metal diode electrical characteristics fabricated on this GOI confirm Ge crystal quality. The selectively grown GOI structure can provide the monolithic integration of SiGe based devices on a Si very large scale integration (VLSI) platform.

Dependence of silicon PIN diode electrical characteristics on proton fluence

A comparative analysis of capacitance–voltage (C–V ) and current–voltage (I–V ) characteristics dependent on proton irradiation fluence in the range from 7·1012 to 7·1014 p/cm2 has been performed in float zone (FZ) silicon PIN diodes. A δ-shape and triangle profiles of radiation induced defects were formed by irradiation with protons having energy in the range from 2.0 to 2.7 MeV. Temperature-dependent variations of current (I–T) at fixed reverse voltage VR enable one to extract the thermal activation parameters. These values are found to be in a quantitative agreement with trap activation parameters measured by DLTS technique. The role of point and extended defects in correlated modifications of C–V and I–V characteristics of the irradiated diodes is discussed. Keywords: radiation defects, Si PIN diodes, capacitance–voltage, current–voltage characteristics

Schottky diodes based on electrospun polyaniline nanofibers: Effects of varying fiber diameter and doping level on device performance

Electrospinning is used to fabricate Schottky diodes using polyaniline nanofibers and n-doped Si. By varying the fiber diameter, and also by varying the fiber doping level at a fixed diameter, we compare the device performance and examine the role of surface states on barrier height and charge transport. The diode electrical characteristics were analyzed using the standard thermionic emission model of a Schottky junction. Clear rectification is observed for diodes fabricated from thick fibers with significantly reduced rectification ratios for diodes fabricated from thinner ones. The surface states on the semiconductor exert a weaker influence on diodes fabricated from thinner fibers due to the reduced junction area, and for the thinnest fiber where the depletion width is expected to be negligible, the analysis suggests an additional charge transport mechanism other than thermionic emission at the junction. On the other hand, varying the fiber doping level lowers the diode rectification ratio but other diode parameters are relatively unaffected.

Liquid phase deposited silicon oxide with lower boron impurity grown on gallium nitride by temperature‐difference method

AbstractThis study investigates the growth of silicon oxide film on gallium nitride using hydrosilicofluoric acid and silica gel by the temperature‐difference liquid‐phase deposition. In the conventional liquid phase deposition, the boric acid is used as fluorine scavenger to prompt silicon oxide deposition and it also acts as an impurity in the oxide film. The better metal–oxide–semiconductor diode electrical characteristics can be obtained by the temperature‐difference method with lower boric acid incorporation and higher deposition rate. Compared with the leakage current density of the conventional and temperature‐difference methods, it can be much improved from 9.93 × 10–2 A/cm2 to 5.8 × 10–4 A/cm2 at +2 MV/cm and from 1.35 × 10–2 A/cm2 to 5.15 × 10–4 A/cm2 at –1 MV/cm. The effective oxide charges is improved from 3.88 × 1011 cm–2 to 2.27 × 1011 cm–2. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

GaSb quantum-well-based “buffer-free” vertical light emitting diode monolithically embedded within a GaAs cavity incorporating interfacial misfit arrays

The authors demonstrate a monolithic, electrically injected, vertically emitting GaSb∕AlGaSb light emitting diode (LED) emitting at 1.6μm comprised of a hybrid GaAs∕GaSb-based structure. The LED is comprised of a GaSb∕AlGaSb quantum well/barrier active region embedded within high index contrast GaAs∕AlGaAs distributed Bragg reflectors (DBRs) using two interfacial misfit (IMF) arrays to relieve the strain induced from the high 8% lattice mismatch between the material systems. The first IMF is formed under compressive strain conditions to enable strain-free, defect-free deposition of GaSb active region directly on the lower GaAs∕AlAs DBRs without need for thick buffer. The second IMF is formed under tensile conditions to enable the upper GaAs∕AlAs DBRs on the GaSb active region. The device demonstrates a maximum output power of 3.5μW. Initial diode optical and electrical characteristics along with IMF band structure are discussed.

Observation of a multilayer planar in-grown stacking fault in 4H-SiC p-i-n diodes

In-grown stacking faults (IGSFs) are planar defects that do not propagate under either an applied optical or electrical bias; however, their effect upon the electrical characteristics of diodes is not well understood. We present evidence for a multilayered IGSF and discuss its electrical and optical characteristics. These IGSFs, despite similar electroluminescence signatures, were observed to act as either a current barrier or as a short between the p+ and n+ layers, causing increases in the leakage current in p-i-n diodes. The difference in conduction behavior is attributed to the nucleation location of the IGSF within the diode drift region.

Technology and electrical properties of ohmic contacts and Schottky diodes on homoepitaxial layers grown on (100) diamond surfaces

A general view of the key issues which have to be surmounted for building elementary devices such as Schottky diodes on homoepitaxial p-type diamond layers is presented. The growth process of double homoepitaxial layers, comprising a stack of both high and low boron doped films, is described and boron concentrations are analysed by means of cathodoluminescence. The methods used for masking, performing lithography on 3 × 3 mm 2 samples and etching are delineated. Several ohmic contacts are compared. Surface treatments necessary for the Schottky diode technology are analysed and discussed. Two methods for achieving adherent Schottky contacts are compared and the electrical characteristics of diodes are studied as a function of the morphology, defect content and doping of the diamond layer, metal stack which is used, temperature history of the sample and passivation post-processes such as dry etching.

Direct growth of GaN on off‐oriented SiC (0001) by molecular‐beam epitaxy for GaN/SiC heterojunction bipolar transistor

Direct growth of GaN on misoriented 4H- and 6H-SiC (0001) Si-face substrates and electrical characteristics of n-GaN/p-SiC heterojunction mesa diodes are presented. GaN was grown by molecular-beam epitaxy (MBE) using elemental Ga and rf plasma-excited active nitrogen. SiC substrates misoriented 8° toward the [11-20] direction were used in this study. The surfaces of MBE-grown GaN layers have wavy features with peak-to-valley height of 30 nm. These features originated from the substrate misorientation. It was found that step bunching and large faceting along [01-10] and [10-10] directions occurred during the growth of GaN. Lowering the growth temperature suppresses large faceting, and results in reduction of the peak-to-valley height to 3 nm. However, the surface still has the same undulating features (on a smaller length scale). Mesa diodes were fabricated from the grown GaN layers. The correlation between the diode electrical characteristics and GaN growth conditions is discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Performance Comparison of Standard and Optimised Clamp Diodes for High Power IGBT Inverters for Traction Applications

In this paper the problem of overvoltages protection in high power IGBT inverters for traction applications is presented. The turn off operation of the voltage clamped IGBT inverter is described. The capability of the clamp circuit in limiting the IGBT turn-off voltage spikes is analysed and the importance of the clamp diode electrical characteristics are pointed out. Finally, experimental and simulated results allow a direct comparison between standard ultrafast clamp diodes and optimised clamp diodes.