Temperature Dependence Of Electrical Characteristics Research Articles

InGaN based Schottky barrier solar cell: Study of the temperature dependence of electrical characteristics

The indium gallium nitride (InGaN) semiconductor alloy shows great promise for high-efficiency thin-film solar cells due to its intrinsic characteristics. However, there are major challenges in the development of high-quality p-doped and indium-rich InGaN layers to fabricate a pn or pin solar cell. This study focuses on the development of an alternative structure, not requiring p-doping, with a Schottky contact on n-type InGaN. The InGaN absorber was grown by metalorganic chemical vapor deposition and its structural, morphological and optical properties studied. Structural analysis by X-ray diffraction showed the growth of single crystal layers without phase separation. Indium compositions which vary up to around 8.3 % were confirmed by transmission measurements. The formation of V-shaped pits was observed with increased indium composition at lower growth temperatures. Schottky diodes based on InGaN with platinum metallic contacts were fabricated and their current–voltage characteristics studied in detail as a function of temperature. This analysis of the conduction mechanisms in Schottky/InGaN devices permitted in particular the extraction of the diode parameters as a function of the temperature showing a high rectification with an ideality factor of 1.15 with reverse saturation current of 6.7×10−9A at room temperature for an indium composition of 5.52 %. In addition, the analysis revealed the presence of a dual Gaussian distribution of barrier heights in a specific temperature range. Finally, the incident photon-to-electron conversion efficiency (IPCE) of the fabricated InGaN Schottky solar cells, measured using intensity-modulated photocurrent spectroscopy, reached a peak value of 51 %, which is among the highest published values for InGaN based solar cells.

Temperature dependence of electrical characteristics of Si-implanted AlN layers on sapphire substrates

AlN with a large bandgap energy is one of the most attractive materials for high-temperature applications. However, performance of AlN devices at high temperatures has been limited by technical problems with electrical characterization systems. Here, we show that Schottky-barrier diodes (SBDs) and metal-semiconductor field-effect transistors with Si-implanted AlN channels can operate at 1100 K and 1000 K, respectively. The breakdown voltage and barrier height of the AlN SBD were 610 V and 3.5 eV, respectively. We found that the high barrier height and thermal stability of the Ni contact on AlN greatly contributed to high-temperature operation of the devices.

Temperature Dependence of Electrical Characteristics of ZnO Nanowire Field-Effect Transistors with AZO and Aluminium Source/Drain Contact

In this study, ZnO nanowire field-effect transistor (FET) with an aluminium-doped ZnO (AZO) and an aluminium (Al) dual layer source and drain contact are fabricated and temperature dependent characteristics in the range of 200 – 300 K are analyzed through experimental measurements. The effect of temperature on threshold voltage, subthreshold slope, transconductance, and field effect mobility are analysed. The transfer curve exhibits a parallel shift toward a negative gate voltage direction with a negative shift of the threshold voltage, an increase in the subthreshold slope, and a field-effect mobility as the temperature rises. The electrical properties of the transistors demonstrate typical behaviour at various temperatures.

Temperature dependence of electrical characteristics and interface state densities of Au/n-type Si structures with SnS doped PVC interface

In this study, the electrical properties of Au/(SnS doped PVC)/n–Si structures were investigated in detail using current/voltage (IV) data in wide temperature range (80–340 K by 20 K steps). Some of the basic electrical parameters such as ideality factor (n), saturation current (I 0), and barrier height (Φ bo ) were obtained. When these parameters were extracted using thermionic emission (TE) theory, it was found that the value of n decreases whereas Φ bo increases with increasing temperature. This result can be explained by the barrier height (BH) inhomogeneity. The observed two linear regions in the plots of Φ bo –n, Φ bo –(1/2kT)1 and (n −1–1)–(1/2kT) in temperature regions of 80–160 K and 80–340 K form an evidence to the presence of Double Gaussian distribution (DGD). Using the plot of Φ bo –(1/2kT), the values of mean BH () and standard deviation (σ S) were found as 0.486 eV and 66 mV for first region, and 0.984 eV and 139 mV for second region, respectively. Thus, the effective Richardson constant (A*) was obtained using the interception point of the modified Richardson plot for these regions as 7.013 × 10−6 A.K−2cm−2 and 88.12 A.K−2cm−2, respectively. It is clear that A* value for second region is closer to theoretical value (=112 A.K−2cm−2 for n–Si). Finally, the energy dependent profile of the surface-states (Nss) was extracted using Card-Rhoderick method and Nss was found to range from ∼1012 (at 80 K) to 1013 eV−1 cm−2 (at 340 K).

Cryogenic Transport Characteristics of P-Type Gate-All-Around Silicon Nanowire MOSFETs

A 16-nm-Lg p-type Gate-all-around (GAA) silicon nanowire (Si NW) metal oxide semiconductor field effect transistor (MOSFET) was fabricated based on the mainstream bulk fin field-effect transistor (FinFET) technology. The temperature dependence of electrical characteristics for normal MOSFET as well as the quantum transport at cryogenic has been investigated systematically. We demonstrate a good gate-control ability and body effect immunity at cryogenic for the GAA Si NW MOSFETs and observe the transport of two-fold degenerate hole sub-bands in the nanowire (110) channel direction sub-band structure experimentally. In addition, the pronounced ballistic transport characteristics were demonstrated in the GAA Si NW MOSFET. Due to the existence of spacers for the typical MOSFET, the quantum interference was also successfully achieved at lower bias.

Temperature Dependence of Electrical Characteristics in Indium-Zinc-Oxide Thin Film Transistors from 10 K to 400 K**Supported by the National Natural Science Foundation of China under Grant No 61574048, the Pearl River S&T Nova Program of Guangzhou under Grant No 201710010172, the International Science and Technology Cooperation Program of Guangzhou under Grant No 201807010006, and the Opening Fund of Key Laboratory

The transfer characteristics of amorphous indium-zinc-oxide thin film transistors are measured in the temperature range of 10–400 K. The variation of electrical parameters (threshold voltage, field effect mobility, sub-threshold swing, and leakage current) with decreasing temperature are then extracted and analyzed. Moreover, the dominated carrier transport mechanisms at different temperature regions are investigated. The experimental data show that the carrier transport mechanism may change from trap-limited conduction to variable range hopping conduction at lower temperature. Moreover, the field effect mobilities are also extracted and simulated at various temperatures.

Temperature dependence of electrical characteristics for diamond Schottky-pn diode in forward bias

A diamond Schottky-pn diode (SPND) was fabricated and its electrical properties were investigated by measuring the current-voltage characteristics. The diode showed high current density (>104 A/cm2 at 7 V) at room temperature with low differential on-resistance (~10−5 Ωcm2) under a wide temperature range (295–600 K). We constructed Richardson plots based on the characteristics and then estimated the potential barrier height on the hole current. From these results combined with the results of Poisson equation analysis, we viewed the change in hole barrier as a function of applied voltage and obtained the value of the hole activation energy as ~0.06 eV in the p+-type layer around the flat-band voltage. We clarified the transport mechanisms of the SPND and the method for estimating the activation energy in heavily boron-doped diamond exhibiting hopping conduction.

Observation of Van Hove Singularities and Temperature Dependence of Electrical Characteristics in Suspended Carbon Nanotube Schottky Barrier Transistors

A Van Hove singularity (VHS) is a singularity in the phonon or electronic density of states of a crystalline solid. When the Fermi energy is close to the VHS, instabilities will occur, which can give rise to new phases of matter with desirable properties. However, the position of the VHS in the band structure cannot be changed in most materials. In this work, we demonstrate that the carrier densities required to approach the VHS are reached by gating in a suspended carbon nanotube Schottky barrier transistor. Critical saddle points were observed in regions of both positive and negative gate voltage, and the conductance flattened out when the gate voltage exceeded the critical value. These novel physical phenomena were evident when the temperature is below 100 K. Further, the temperature dependence of the electrical characteristics was also investigated in this type of Schottky barrier transistor.

Temperature Dependence According to Grain Boundary Potential Barrier Variation in Vertical NAND Flash Cell with Polycrystalline-Silicon Channel.

We investigate the electrical characteristics according to changing temperature on trap distribution in the energy gap of grain boundary (GB) and interface trap density (D(it)) between polycrystalline-silicon (poly-Si) channel and tunnel oxide in Vertical NAND (VNAND) flash cell with poly-Si channel. We confirmed that there are two factors changing GB potential barrier height such as trap distribution in GB and D(it) using technology computer-aided design (TCAD) simulation. Also, we found that the electrical characteristics according to changing temperature are significantly dependent on height and position of GB potential barrier in VNAND flash cell with poly-Si channel. We expect that it is required to develop more accurate extraction method for trap distribution in each GB and D(it) for better understanding temperature dependence of electrical characteristics in VNAND Flash cell.

Temperature dependence of electrical characteristics of n-InxGa1 − xN/p-Si hetero-junctions made totally by RF magnetron sputtering

The n-InxGa1−xN/p-Si hetero-junction diodes including their semiconductors and electrodes were grown directly on p-Si (100) wafer by magnetron sputtering. Targets for n-InxGa1−xN films with x=0, 0.15, and 0.4 were made by hot pressing with the mixture of metallic and nitride powders. SEM, AFM, and Hall measurement were carried out to analyze the surface morphology, topography, and electrical property of the n-InxGa1−xN films. Temperature dependent transport behavior of n-InxGa1−xN/p-Si hetero-junction diodes was determined by the I–V analyses. After measurements at room temperature, the turn-on voltage and ideality factor were determined to be 2.1V, 6.2 for n-GaN/p-Si, 1.8V, 5.2 for n-In0.15Ga0.85N/p-Si, and 1.4V, 4.3 for n-In0.4Ga0.6N/p-Si, respectively. In addition, with a 1mm2 contact of all devices, the current densities at 20V and the leakage current densities at −5V were calculated to be 0.183 and 5.96×10−5A·cm−2 for n-GaN/p-Si, 0.303 and 8.05×10−5A·cm−2 for n-In0.15Ga0.85N/p-Si, and 0.513 and 2.81×10−4A·cm−2 for n-In0.4Ga0.6N/p-Si. Our three devices strongly sustained under reverse bias and showed the breakdown voltage beyond 20V. The variations of electrical properties with the test temperature were also investigated up to 150°C. The barrier height, ideality factor, and series resistance of all hetero-junction diodes were also calculated by using equations based on the standard thermionic-emission (TE) mode and Cheung's method.

Quantitative analyses of damp-heat-induced degradation in transparent conducting oxides

A complete understanding of the reliability for ZnO-based transparent conducting oxides is essential for actual applications in photovoltaic devices or displays requiring long-term stability. The stability and degradation mechanisms under a controlled damp-heat environment (humid and hot atmosphere) for sputter-deposited aluminum-doped zinc oxide (ZnO:Al) thin films were quantitatively studied. The continuous degradations of carrier concentration and mobility with the Fermi-level shift were observed, and this behavior was resolved by separating the changes in the carrier-transport characteristics of the intragrain and grain boundary. By correlating the temperature dependence of electrical characteristics with x-ray photoelectron spectroscopy, the degradation is well explained by the increase of chemisorbed OH− in the grain boundaries.

Temperature dependence of electrical characteristics of Pt/GaN Schottky diode fabricated by UHV e-beam evaporation

Temperature-dependent electrical characterization of Pt/n-GaN Schottky barrier diodes prepared by ultra high vacuum evaporation has been done. Analysis has been made to determine the origin of the anomalous temperature dependence of the Schottky barrier height, the ideality factor, and the Richardson constant calculated from the I-V-T characteristics. Variable-temperature Hall effect measurements have been carried out to understand charge transport at low temperature. The modified activation energy plot from the barrier inhomogeneity model has given the value of 32.2 A/(cm2 K2) for the Richardson constant A** in the temperature range 200 to 380 K which is close to the known value of 26.4A/(cm2 K2) for n-type GaN.

Temperature Dependence of Electrical Characteristics of Strained nMOSFETs Using Stress Memorization Technique

The temperature dependence of the electrical characteristics of strained nMOSFETs combining stress memorization technique (SMT) process and contact etch-stop layer has been investigated. The observed higher mobility and lower gate tunneling current of SMT devices indicate higher tensile stress in the channel and prove the true transmission of SMT-process-induced stress from the deposited SiN layer. Moreover, as temperature is increased, SMT devices show less deteriorated mobility and increased gate tunneling current, which are due to decreased phonon scattering and increased tunneling barrier height, respectively.

Features of the mechanism of electrical conductivity of semiinsulating CdTe crystals

Temperature dependence of electrical characteristics of p-CdTe semi4nsulating single-crystals are studied, and substantial features of their electrical conductivity not described in available publications are revealed. The activation energy of the p-type conduction material close to the intrinsic one can be both lower and higher than the half-width of the band gap of semi conductor. The results of the analysis of statistics of electrons and holes based on the electroneutrality equation showed that the observed features of electrical properties of the material can be interpreted based on the specific features of compensation processes. The procedure of determining the ionization energy and degree of compensation of acceptors responsible for electrical conductivity of the material is suggested. It is shown that, in the limits of climatic temperature variations, inversion of the conduction type can be observed, and, as a consequence, the Schottky contact can disappear in the CdTe-based detector of the X-ay and γ radiation.

Operational amplifiers operating in temperature range from 300 to 4.2 K

We present preamplifiers for frequencies from dc to few 10 MHz operating over temperature range from 300 to 4.2 K. Typical application of these circuits which use CMOS operational amplifiers is to match high impedance cryogenic sensors with low impedance cables to lead out a signal to room temperature electronics without bandwidth limiting while preserve signal to noise ratio and linearity. Temperature dependence of electrical characteristics is shown including dissipated power and input voltage noise density spectra.

Electrical behaviour of Al/SiGe/Si heterostructures: effect of surface treatment and dislocations

The effect of HF and H 2SO 4 + H 2O 2 treatments on the electrical behaviour on Al/n-SiGe junctions prepared by MBE on n-Si substrates were studied. Barrier heights of 0.73 ± 0.03 eV and 0.46 ± 0.04 eV, respectively, were obtained. Misfit dislocations located at the SiGe/Si interface yielded different anomalies of the electrical behaviour, as excess currents, instabilities, and anomalous temperature dependence of electrical characteristics and evaluated parameters. It is shown that in spite of anomalies, the electrical measurements can provide useful and reliable information about the structures.

Theoretical study of the temperature dependence of electrical characteristics of Schottky diodes with an inverse near-surface layer

Counter-doping of a near-surface layer is a well-known method of Schottky barrier height engineering. However, the temperature dependence of the electrical characteristics of such structures has not been studied until now. In this work, we present the results of our theoretical study of the temperature dependence of the Schottky diode parameters. The drift-diffusion approximation was used for the calculation of I– V and C– V characteristics and the thermionic emission theory for the extraction of diode parameters. This procedure gave results in agreement with the results observed on the experimental structures. The barrier height decreases with decreasing temperature. All simulated I– V curves for the different temperatures have an almost common cross-point at certain voltage which depends on the doping concentrations and thickness of the counter-doped layer. The fact that this effect is not currently observed in experiments is probably caused by the fact that the series resistance of real structures consists of more components not only from ohmic resistance of the semiconductor bulk. For the voltage of the cross-point, the diode current is temperature independent.

Punchthrough behavior in short channel NMOS and PMOS 6H-silicon carbide transistors at elevated temperatures

An experimental investigation of the effects of high temperature on short channel NMOS and PMOS transistors in 6H-SiC is reported. Punchthrough characteristics are presented and examined at room temperature and 300/spl deg/C. The punchthrough current increases dramatically for scaled PMOS transistors at high temperature while the temperature dependence of electrical characteristics for short channel NMOS is small. The results presented in this paper also provide insight into design criteria for short channel silicon carbide (SiC) devices intended for operation at elevated temperatures.

Hopping conduction in SiO2 films containing C, Si, and Ge clusters

Temperature dependence of electrical characteristics of SiO2 films doped with C, Si, and Ge were studied. The conductivity σ was found to vary with the temperature as lnσ∝T−1/4 over a wide temperature range, indicative of the conduction by the variable range hopping (VRH) mechanism. Since the previous optical studies for the same films indicate the existence of clusters in the films, it is very likely that the VRH through localized states associated with clusters dominates the conduction process, irrespective of the kind of group IV elements.

Diode characteristics and residual deep-level defects of p+n abrupt junctions fabricated by rapid thermal annealing of boron implanted silicon

p+n diodes were fabricated by rapid thermal annealing (RTA) of boron implanted silicon (75 keV, 2*1016 cm-2) in the annealing temperature range 700-1100 degrees C for around 7 s, and the RTA temperature dependence of electrical characteristics of these diodes was studied. Deep-level transient spectroscopy (DLTS) measurements were made to evaluate residual deep-level defects in the n-type bulk. Three electron traps E1 (Ec-0.21 eV), E2 (Ec-0.23 eV) and E3 (Ec-0.29 eV) were observed in p+n diodes fabricated by RTA at 700 degrees C. It was considered that these three traps were residual point defects near the tail of the implantation damage after RTA. Residual defect concentrations increased in the range 700-900 degrees C and decreased in the range 1000-1100 degrees C. The growth of defects in the bulk was ascribed to the diffusion of defects from the implanted layer during RTA. Concentrations of E4 (Ec-0.33 eV) and E5 (Ec-0.48 eV) observed in p+n diodes fabricated by RTA at 1100 degrees C were approximately 1012 cm-3. It was found that these residual deep-level defects observed by DLTS were inefficient generation-recombination centres since the reverse current was independent of the RTA temperatures.