Search

Device surface properties are critical for its performance such as channel electron density, leakage current, subthreshold swing (SS), and noise in gallium nitride high-electron-mobility transistors (HEMTs). In this article, the improved surface property of InAlN/GaN HEMTs with forming gas (FG, 5% H2, and 95% N2) annealing is demonstrated. X-ray photoelectron spectra (XPS) show that the number of Ga–O bonds decreases while that of the Ga–N bonds increases, an indication of the surface native oxide removal after FG annealing. Compared with N2 annealing, an increase of two-dimensional electron gas (2DEG) electron density with FG annealing is determined by both energy band simulation and capacitance–voltage measurement. Transmission line measurement (TLM) shows that N2 annealing offers a lower ohmic contact resistance ( ${R}_{\text {C}}$ ) while FG annealing features a lower sheet resistance ( ${R}_{\text {sheet}}$ ). Herein, a FG/N2 two-step ohmic contact annealing is developed to achieve a SS of 110 mV/dec, a transconductance ( ${g}_{\text {m}}$ ) peak of 415 mS/mm, a record low drain-induced barrier lowing (DIBL) of 65 mV/V, and a record high power gain cutoff frequency ( ${f}_{\text {max}}$ ) of 270 GHz on a 50-nm InAlN/GaN HEMT on Si.

We investigated the rapid thermal annealing (RTA) sequence effect on the electrical, optical, morphological, and structural properties of transparent thin film transistors (TTFTs) with an indium gallium zinc oxide (IGZO) channel and an indium tin oxide (ITO) source/drain. The electrical and optical properties of the IGZO channel and the ITO source/drain electrodes were compared as a function of RTA temperature in ambient air. The performance of a TTFT with only an RTA-processed IGZO channel was compared with that of a TTFT with an RTA-processed IGZO channel and ITO source/drain electrodes. Using the circular transmission line measurement (CTLM) method, we suggest a possible mechanism that explains the effect of the RTA process on the performance of the TTFT with only an annealed IGZO channel vs. that with an annealed IGZO/ITO multilayer. The TTFT with an RTA-processed IGZO/ITO multilayer showed a threshold voltage shift, an improved on/off ratio of 3.54 × 1011, a subthreshold swing of 0.33 V/decade, and a high mobility of 8.69 cm2/V·s. This indicates that simultaneous RTA processing for an IGZO channel and an ITO electrode is beneficial for the fabrication of high-performance TTFTs.

Vertical III-V nanowire MOSFETs have demonstrated excellent performance including high transconductance and high ${I}_{\text {on}}$ . One main bottleneck for the vertical MOSFETs is the large access resistance arising from the contacts and ungated regions. We demonstrate a process to reduce the access resistance by combining a gate-last process with ALD gate-metal deposition. The devices demonstrate fully scalable ${g}_{\text {m}}$ down to ${L}_{\text {g}} =25$ nm. These vertical core/shell InAs/InGaAs MOSFETs demonstrate ${g}_{m} =3.1$ mS/ $\mu \text{m}$ and ${R}_{\text {on}} = 190\,\,\Omega \mu \text{m}$ . This is the highest ${g}_{\text {m}}$ demonstrated on Si. Transmission line measurement verifies a low contact resistance with ${R}_{\text {C}} = 115\,\,\Omega \mu \text{m}$ , demonstrating that most of the MOSFET access resistance is located in the contact regions.

Al/InGaAs, Al/Ti/InGaAs, and Al/Ni/InGaAs contacts were prepared by conducting rapid thermal annealing at different temperatures, and the interfacial reaction was characterized using x-ray diffraction, atomic force microscopy, and transmission electron microscopy. The specific contact resistivity of the metal film contacts on n-InGaAs was determined using a circular transmission line measurement. The Al/Ni/InGaAs, Al/Ti/InGaAs, and Al/InGaAs stack contacts remained stable even after the samples were subjected to annealing at 400°C. When the annealing temperature increased to 600°C, Al began melting and clustering due to the formation of Al(Ga) to form Al/InGaAs. An AlNi phase was formed at the interfaces of an Al/Ni/InGaAs contact when it was annealed above 400°C, thus causing the specific resistance and roughness to increase dramatically. Each element of the Al/Ti/InGaAs contact began diffusing when it was annealed beyond 400°C, and an Al3Ti phase was formed above 500°C. The formation of Al3Ti led to the increase in the specific resistance and roughness. Moreover, the as-deposited Al/Ni/InGaAs, Al/Ti/InGaAs and Al/InGaAs samples had specific resistances of 1.11 × 10−5 Ω cm2, 5.11 × 10−5 Ω cm2, and 1.14 × 10−4 Ω cm2, respectively. These results reveal that to develop the Al/Ti/InGaAs and Al/Ni/InGaAs stacks on InGaAs with a low parasitic resistance, the processing temperature should be lower than 400°C.

Here we evaluate in-situ Ga doping of SiGe as an alternative to ex-situ ion implantation for source/drain contact formation. Si0.5Ge0.5 layers are grown on an ASM Intrepid ES high volume CVD reactor and co-doped with B and Ga. A circular transmission line measurement (CTLM) comparison of SiGe:B and SiGe:B:Ga is presented and we report a statistically significant improvement in contact resistivity with the addition of Ga. The Ti/SiGe contacts formed with the B-doped sample had an average ρc ~ 9 x 10-9 Ω-cm2 while the best Ga/B co-doped sample yielded an average ρc ~ 2.5 x 10-9 Ω-cm2. We also evaluate the epitaxial growth on fin patterned wafers and we are able to demonstrate high crystalline quality SiGe:Ga layers without loss of selectivity on the dielectric areas of the wafer.

This study determined the top (vertical) and edge (horizontal) resistivities of metal–MoS2 contact based on the experimental results obtained using the transmission line measurement structure. A novel two-step sulfurization scheme was conducted for forming Nb-doped MoS2 films on a sapphire substrate. The edge contact resistivity, $\rho _{C\_{}{\textit {edge}}}$ , was almost two orders of magnitude lower than the top contact resistivity, $\rho _{C\_{}{\textit {top}}}$ . Our findings highlight a simple and effective method to accurately determine the edge and top contact resistances of a metal–two-dimensional material contact.

In this work, we observe the distinct V TH characteristics in the Au-free gate-first processing p-GaN/AIGaN/GaN HEMTs with two commonly used passivation layers, i.e., SiN and SiO 2 . The device with SiN shows a depletion-mode (D-mode) characteristic (V TH ,. .., -5V) whereas the device with SiO 2 passivation exhibits an enhancement-mode (E-mode) characteristic (VTH, ..., +0.7V). Furthermore, Transmission Line Measurement (TLM) devices are fabricated to investigate the effects of the passivation on two dimensional electron gas (2DEG) in p-GaN/AIGaN/GaN stack. The results indicate that a low Rsh is obtained while passivating device surface with SiN layer, suggesting that 2DEG is present, which is most probably due to an unfunctional p-GaN layer. The SIMS results indicate a high H−intensity in the p-GaN/AIGaN/GaN stack with a SiN passivation layer. Thus, P-GaN deactivation due to the formation of complex Mg-H after SiN passivation is proposed to explain the D-mode characteristic in the device with a SiN passivation layer.

Light-induced electroless plating (LIEP) is an easy and inexpensive method that has been widely used for seed layer deposition of Nickel/Copper (Ni/Cu)-based metallization in the solar cell. In this study, material characterization aspects of the Ni seed layer and Ni silicide formation at different bath conditions and annealing temperatures on the n-side of a silicon diode structure have been examined to achieve the optimum cell contacts. The effects of morphology and chemical composition of Ni film on its electrical conductivity were evaluated and described by a quantum mechanical model. It has been found that correlation exists between the theoretical and experimental conductivity of Ni film. Residual stress and phase transformation of Ni silicide as a function of annealing temperature were evaluated using Raman and XRD techniques. Finally, transmission line measurement (TLM) technique was employed to determine the contact resistance of Ni/Si stack after thermal treatment and to understand its correlation with the chemical-structural properties. Results indicated that low electrical resistive mono-silicide (NiSi) phase as low as 5 mΩ.cm2 was obtained.

Al0.23Ga0.77N/GaN and Al0.27Ga0.73N/GaN epitaxial layers were grown on sapphire substrates by metal organic chemical vapour deposition (MOCVD). The in-plane strain (exx) values were found to be -2.4 ×10-4 and -2.8 ×10-4 for Al0.23Ga0.77N and Al0.27Ga0.73N layers using asymmetric reciprocal space mapping (RSM). Surface morphology and emission properties of the samples were analysed using atomic force microscopy (AFM) and photoluminescence spectroscopy (PL) respectively. Circular Transmission Line Measurement (CTLM) technique was adopted to find the variation in contact resistance (Rc), transfer length (LT) and specific contact resistance (ρc) between metal contacts (Ti/Al/Ni/Au: 200/1000/200/1000 A) and AlxGa1-xN layers.A minimum specific contact resistance, ρc of about 7.81x10-6 Ωcm2 was obtained for Ti/Al/Ni/Au contact on the Al0.23Ga0.77N layer. The device characteristics were correlated with the structural and surface quality of AlxGa1-xN layers.

Highly doped n-Al0.6Ga0.4N can be used to form tunnel junctions (TJs) on deep ultraviolet (UVC) LEDs and markedly increase the light extraction efficiency (LEE) compared to the use of p-GaN/p-AlGaN. High quality Al0.6Ga0.4N was grown by NH3-assisted molecular beam epitaxy (NH3 MBE) on top of AlN on SiC substrate. The films were crack free under scanning electron microscope (SEM) for the thickness investigated (up to 1 µm). X-ray diffraction reciprocal space map scan was used to determine the Al composition and the result is in close agreement with atom probe tomography (APT) measurements. By varying the growth parameters including growth rate, and Si cell temperature, n-Al0.6Ga0.4N with an electron density of 4×1019 /cm3 and a resistivity of 3 mΩ·cm was achieved. SIMS measurement shows that a high Si doping level up to 2×1020 /cm3 can be realized using a Si cell temperature of 1450 °C and a growth rate of 210 nm/hr. Using a vanadium-based annealed contact, ohmic contact with a specific resistance of 10−6 Ω·cm2 was achieved as determined by circular transmission line measurement (CTLM). Finally, the n-type AlGaN regrowth was done on MOCVD grown UVC LEDs to form UVC TJ LED. The sample was processed into thin film flip chip (TFFC) configuration. The emission wavelength is around 278 nm and the excess voltage of processed UV LED is around 4.1 V.

In this report, the thermal performance of a hydrogen (H)-terminated diamond field-effect transistor (FET) is investigated using Raman spectroscopy and electrothermal device modeling. First, the thermal conductivity (κdiamond) of the active diamond channel was determined by measuring the temperature rise of transmission line measurement structures under various heat flux conditions using nanoparticle-assisted Raman thermometry. Using this approach, κdiamond was estimated to be 1860 W/m K with a 95% confidence interval ranging from 1610 to 2120 W/m K. In conjunction with measured electrical output characteristics, this κ was used as an input parameter for an electrothermal device model of an H-terminated diamond FET. The simulated thermal response showed good agreement with surface temperature measurements acquired using nanoparticle-assisted Raman thermometry. These diamond-based structures were highly efficient at dissipating heat from the active device channel with measured device thermal resistances as low as ∼1 mm K/W. Using the calibrated electrothermal device model, the diamond FET was able to operate at a very high power density of 40 W/mm with a simulated temperature rise of ∼33 K. Finally, the thermal resistance of these lateral diamond FETs was compared to lateral transistor structures based on other ultrawide bandgap materials (Al0.70Ga0.30N, β-Ga2O3) and wide bandgap GaN for benchmarking. These results indicate that the thermal resistance of diamond-based lateral transistors can be up to ∼10× lower than GaN-based devices and ∼50× lower than other UWBG devices.

Ni/Au contacts to p-GaN were studied as a function of free hole concentration in GaN using planar transmission line measurement structures. All contacts showed a nonlinear behavior, which became stronger for lower doping concentrations. Electrical and structural analysis indicated that the current conduction between the contact and the p-GaN was through localized nano-sized clusters. Thus, the non-linear contact behavior can be well explained using the alloyed contact model. Two contributions to the contact resistance were identified: the spreading resistance in the semiconductor developed by the current crowding around the electrically active clusters, and diode-type behavior at the interface of the electrically active clusters with the semiconductor. Hence, the equivalent Ni/Au contact model consists of a diode and a resistor in series for each active cluster. The reduced barrier height observed in the measurements is thought to be generated by the extraction of Ga from the crystalline surface and localized formation of the Au:Ga phase. The alloyed contact analyses presented in this work are in good agreement with some of the commonly observed behavior of similar contacts described in the literature.

In this paper, we report the fabrication of heterojunction carrier selective c-Si solar cell using a hole selective poly – 3,4 ethylene dioxythiophene (PEDOT:PSS) and an electron selective magnesium fluoride (MgF2) layers. Dopant- free asymmetric heterojunction solar cells (DASH cells) based on c-Si have gained considerable attention due to low-cost fabrication methods and ease of fabrication techniques. Carrier selective contact (CSC) based solar cells can reduce the interface recombination by selectively allowing only one type of carriers to pass through the selective layers. Here, solution-processed hole selective PEDOT:PSS was spin-coated on the c-Si, while the electron selective MgF2 layer was deposited by thermal evaporation technique. The conductivity of the PEDOT:PSS film was enhanced using secondary solvent doping with DMSO. The thickness of the MgF2 layer was optimized using the transmission line measurement. The dipole behavior of MgF2 would result in a decrease in the effective work function of the MgF2/metal stack. The as- fabricated solar cell showed a power conversion efficiency of 7.6% with an open-circuit voltage of 550 mV and a short circuit current of 31 mA/cm2.

Accurate simulation and modelling is a very important aspect in designing a wearable antenna. In some cases, due to the complexity and non-homogenous properties of an electro-thread structure, the radiating element of the antenna is sometimes modelled as a perfect metallic surface, which is not the exact representative of the actual electro-thread and may cause deviation between simulation and measurement results. However, it is known that the exact fabric pattern and thread structure are very difficult to be physically modelled and designed. In order to reduce the uncertainties and the inaccuracy factors, the modelling of electro-textile in electromagnetic solver is reduced to bulk conductivity parameter of the radiating element. Therefore, an accurate method to measure the exact conductivity of a new or self-developed textile material, specifically for radio frequency application shall be determined. In this paper, a new technique is adopted to characterize the material’s electrical properties. This method is based on the measurement of scattering parameters, S21 of a two-port transmission line to determine the conductivity of any conductive textiles that are normally used in wearable antenna design. Here, the experiments were performed for two test samples; printed copper as the control sample and off-the-shelf conductive textile known as ShieldIt Super. Both samples were fabricated on a low-loss substrate, Rogers RO5880 having a very low dielectric loss of 0.0009 and dielectric constant of 2.2. The behavior and performance of these two samples operating at 2.45 GHz were investigated and studied in this paper through measurement and detailed simulation. As a result, the calculated conductivity derived from the theoretical transmission line equation based on the scattering parameter data and the substrate’s low-dielectric-loss-approximation was found to be very close to the expected conductivity values. Therefore, this method seems to be more reliable than the I-V curve measurement that was normally used for typical electronic application. However, specifically for radio frequency application, the reliability of the proposed technique shall be verified further especially in terms of its frequency range.

International audience; This work presents a comparative study of conventional and slow wave (SW) transmission lines implemented in an advanced 22-nm CMOS process. Both microstrip (MS) and coplanar waveguides (CPW) were analysed through simulations and measurements. A classical SW approach was used for the implementation of the SW CPWs while the SW effect was generated in the MS lines using bed of nails integrated in the CMOS process. As a proof of concept, the proposed SW MS approach was employed to design a new artificial quarter-wave TL section. The proposed configuration was created loading a meandered MS line with open ended S-MS stubs acting as discrete capacitive loads. Results show that the proposed methodology offers an attractive form factor and good performance.

The electrical performance of a photovoltaic (PV) module is greatly hindered by the existence of parasitic resistance losses, such as high series resistance (R s ) and low shunt resistance (R sh ). Contact resistance at metal grid/semiconductor interface and emitter sheet resistance are two major contributors to cell R s . Transmission Line Measurement (TLM) is a powerful method to estimate these resistance components. This paper presents the application of the TLM method to the cell strips extracted from field-aged PV modules at two different climates (Arizona and Florida) of the same design to investigate the influence of encapsulant material and microcracks on the contact resistivity and sheet resistance of the solar cell. The cells were initially extracted from the module laminate by dissolving the encapsulant polymer in trichloroethylene (TCE) solvent at 80oC for around 3 hours. The recovered cell was then used to cut into rectangular strips of 1.5 cm wide. The effective contact resistivity and emitter sheet resistance between two fingers in each strip were measured and compared to quantify the contact degradation induced from longer field aging. The Arizona module suffered from higher resistance as compared to the Florida module due probably to longer field exposure and higher operating temperatures. This method serves as a good diagnostic tool to anticipate and understand the severity of the contact degradation of solar cells in the fielded modules.

In this letter, the Metal-Insulator-Semiconductor (MIS) contacts are fabricated on the GaN substrates and compared to the Metal-Semiconductor (MS) contacts. To alleviate the Fermi level pinning effect at the Metal-Semiconductor interface, an Al 2 O 3 interfacial layer (IL) (1 ~ 3 nm) is used to form the MIS contacts. By comparing the electrical characteristics, the contact with 0nm Al 2 O 3 layer, i.e., MS contact, shows a lowest current compared to the contacts with an Al 2 O 3 IL, i.e., MIS contact. Furthermore, the current at 0.5V in the fabricated Transmission Line Measurement (TLM) device with 1nm Al 2 O 3 IL is 103 times higher the one without an Al 2 O 3 IL. This proves that inserting an Al 2 O 3 IL could mitigate the Fermi level pinning, resulting in a low Schottky barrier height. Finally, based on the TLM analysis, the resistivity of 5.1×10−4 Ω.cm2 is demonstrated in the MIS contact with 1nm Al 2 O 3 IL.

Measuring and understanding the interfacial resistance between the electrode and electrolyte are critically important for fabricating high-performance thermoelectrochemical cells. Although the charge transfer resistance and other resistance, such as the mass transfer resistance, may measure via electrochemical impedance spectroscopy, the resolution of the charge transfer semicircle in the Cole–Cole plot can decrease if these resistance values are smaller than the solution resistances. Moreover, a small dataset at a very low frequency can affect the analysis results. In this study, the transmission line measurement was applied, which is used in semiconductor physics to determine the contact resistance between a metal and a semiconductor, to thermoelectrochemical cells for simultaneously determining the interfacial and solution resistances. This method was used to quantify the direct-current interfacial and solution resistances, which are directly linked to the power output of cells under different temperatures. Because of a wide applicable concentration range, the interfacial reaction rate constant at high electrolyte concentration could be calculated from the transmission line measurement. Through a comparison with electrochemical impedance spectroscopy results, we concluded that the interfacial resistance is dominated not by the charge transfer resistance but by the mass transfer resistance, which could be dependent on the surface energy of the electrodes.

A classic method for measuring the propagation constant of transmission lines is the one proposed by Bianco and Parodi more than four decades ago [1]. It is based on the invariance of the cross ratio of four complex numbers under a bilinear transformation. This means that it is possible to extract the value of the propagation constant (both real and imaginary parts) of an arbitrary transmission line (TL) by measuring, through an arbitrary (and unique) two-port, the input reflection coefficient of four TL sections of different lengths provided they are terminated by the same load. The accuracy of the original method can be greatly improved by measuring a higher number of TL sections and taking all the possible combinations of four lines. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

Proper thin film transistor (TFT) operation requires that its contact resistance Rc remains only a fraction of its channel resistance Rch. The integration of thin films based on latest generation organic semiconductors into downscaled TFTs with short channel length and high capacitance dielectric results in devices with very low Rch. Matching this with a low enough Rc is very challenging, due to the notoriously poor charge injection into organic semiconductors. The viability of integrated circuit technologies based on organic TFTs hinges on solving this critical contact resistance issue. To properly address this, it is important to use a common metric based on simple, comparable contact resistance measurements. Rc is commonly measured using the Transfer Length Method (TLM) that involves the characterization of TFTs of different channel lengths in the linear regime. We find, however, that the precision and the absolute value of the extracted Rc is greatly influenced by the conditions used to characterize each TFT. This seriously complicates the comparison to other literature values. In this talk, we present an in-depth study of the TLM technique aimed at solving these particular problems. Our TLM structures are based on high mobility organic TFTs, fabricated with different technologies and topologies. We conduct a systematic comparison of voltage- and current-controlled measurements with constant lateral electric field and charge density. As a result, we delineate the conditions to conduct TLM characterization and data treatment for clean Rc extraction. We also identify the measurement parameters that count in establishing a good Rc benchmark.

International audience; Despite their potential in the field of power electronics, many reliability issues still affect the electrical performance of Gallium Nitride HEMT power devices and require an effort of analysis and understanding. The characterization of the on-state resistance of this transistor is necessary to understand the dynamics of some phenomena such as trapping. The degradation of this resistance has always been related to traps in the 2DEG channel, without taking into consideration possible contributions from the source and drain contacts (metal/ semiconductor). In this work, resistance measurements, with and without ultraviolet illumination, are performed on three different technological options to highlight the effect of illumination on contact resistances.

Thin film crystalline silicon (c-Si) solar cells have been a potential candidate to reduce the capital expenditure associated with traditional silicon photovoltaic market. This paper presents the sputtered NiO$_{\mathbf {x}}$ to be a potential candidate as hole-selective layer for c-Si solar cell contacts. NiO$_{\mathbf {x}}$ has a very small valence band offset (VBO $) ( \sim 0.1$ eV) and a large conduction band offset (CBO) with Si $( \sim 2$ eV), which makes it a promising candidate for hole-selective interlayer materials to reduce the contact recombination. In this paper, the effect of annealing condition on the NiO$_{\mathbf {x}}$/Si interface quality is first evaluated by Hall resistivity measurement. Also, the transport of both majority and minority carriers due to NiO$_{\mathbf {x}}$/Si band alignment is investigated by transmission line measurement. Results in this paper show that the sputtered NiO$_{\mathbf {x}}$ can be an effective interlayer material for thin film c-Si solar cell contacts.

We present the characterization of amorphous silicon/aluminum carrier-selective contacts in both front- and rear-emitter configurations, where the aluminum makes direct contact with the doped a-Si:H layers in silicon heterojunction solar cells. The resistance and passivation quality of these contacts have been measured using the transmission line measurement and the quasi-steady-state photoconductance techniques, respectively. The thickness of the doped a-Si:H layer in direct contact with the aluminum is 20 nm and post-aluminumsputtering annealing temperature ranges from 150-240 °C. Samples with aluminum on an a-Si:H(n) layer annealed at 180°C had a contact resistivity below 1 mΩcm2 while the lifetime remained at 4.8 milliseconds– essentially unchanged from the pre-sputtered, passivated sample. These values are superior to those for the traditional silicon heterojunction contact with a transparent conductive oxide layer and can enable devices with low resistive losses and tremendous optical properties through the insertion of a low-refractive index dielectric material at a wellchosen contact fraction.

Catalyst-free, very long InAs nanowires (NWs) are grown on a Si (111) substrate by using metal-organic chemical vapor deposition (MOCVD) system and their growth mechanism is studied. The NW height increases very fast in the beginning of the growth because of the mass-transport contribution of the adatoms from the substrate surface to the NW tip. Then, the NWs grow slowly and consistently until their height exceeds 50 μm. The NW diameter is very uniform along the growth axis regardless of the NW height and this clearly differs from that of the NWs grown via the self-catalyzed vapor–liquid–solid method. A transmission line measurement (TLM) is performed on the very long InAs NW to measure the contact resistance between the NW and the metal electrode. The electrical properties of the NW are further examined. The catalyst-free, very long InAs NWs demonstrated here can be used for an interconnection of the nanoelectronic device array by integrating multiple devices on a single NW.

The Nicolson-Ross-Weir (NRW) method is a classic technique for the measurement of complex permittivity and permeability of materials at RF and microwave frequencies. The method is based on the measurement of transmission and reflection coefficients of the material under test and subsequently, extracting the material parameters through a non-linear inversion process. The NRW method has a limitation on the thickness of the sample to be less than λ/2. The Stepwise NRW method that relies on seeking the correct branch in the inversion process, overcomes the limitation on the thickness on the sample. Both the methods rely on the reflection and transmission coefficients, which is obtained from two-port S-parameters measurements, by inserting the material under test inside a transmission line. In this work, a coaxial airline is used for the transmission line measurement. The de-embedding of the S-parameters, to obtain the reflection and transmission coefficients, requires the position/location of the sample inside the coaxial airline. This can potentially introduce errors due to position uncertainties. We propose a technique to estimate the position of the material under test inside the coaxial airline that eliminates inaccuracies due to positioning errors in the extraction process. The proposed technique relies on the symmetry of S-parameters to estimate the errors in the position of the material placed inside the coaxial airline. Subsequent de-embedding of S-parameters is performed taking into account the estimated error in the position of the material under test. Measurements and investigations are performed using both the NRW and stepwise NRW techniques illustrating the improvement in the accuracy of the measured material parameters.

We show a method for making a self-aligned selective emitter by annealing aluminum grid lines above the SiAl eutectic temperature, and study the recombination properties using lifetime measurements. The dark saturation current density at the metal contact (J0,metal) is determined as a function of minority carrier density using photoconductive decay. After annealing at 600 °C, J0,metal decreases from 1800 fA cm-2 to 500 fA cm-2 at an injection level of 1E15 cm-3. This value of J0,metal would correspond to a very low emitter recombination contribution of ~10 - 25 fA cm-2 for a front metal grid with area coverage of 2 - 5%. In addition, J0,metal is found to be injection dependent. A low contact resistivity of ~0.1 mOhm cm-2 is obtained from transmission line measurement (TLM).

We investigate the channel length dependence of the electrical characteristics of chemical vapor transport (CVT)-grown MoS 2 nanoribbon (NR) Schottky barrier field-effect transistors to provide insights into the transport properties of such nanostructures. The MoS 2 NRs form spontaneously during the CVT growth, without the application of etching. Back gated transmission line measurement FETs were fabricated on a 45 μ m-long NR with channel lengths ranging between 200 nm and 3 μ m. Contact and sheet resistances were extracted from the electrical measurements and their back-gate bias dependence was analyzed. Numerical modeling based on a virtual probe approach combined with the Landauer formalism shows excellent agreement with the measurements. The model enables a quantitative extraction of the intrinsic FET properties, e.g., mean-free-path and electron mobility, and their dependence on carrier density and investigation of plausible trap distributions. A record electron mobility for a MoS 2 NR channel of ∼ 81 cm 2 / V s was achieved.We investigate the channel length dependence of the electrical characteristics of chemical vapor transport (CVT)-grown MoS 2 nanoribbon (NR) Schottky barrier field-effect transistors to provide insights into the transport properties of such nanostructures. The MoS 2 NRs form spontaneously during the CVT growth, without the application of etching. Back gated transmission line measurement FETs were fabricated on a 45 μ m-long NR with channel lengths ranging between 200 nm and 3 μ m. Contact and sheet resistances were extracted from the electrical measurements and their back-gate bias dependence was analyzed. Numerical modeling based on a virtual probe approach combined with the Landauer formalism shows excellent agreement with the measurements. The model enables a quantitative extraction of the intrinsic FET properties, e.g., mean-free-path and electron mobility, and their dependence on carrier density and investigation of plausible trap distributions. A record electron mobility for a MoS 2...

The effect of self-heating and polarisation is studied in AlGaN/GaN Transmission Line Measurement (TLM) structures with varying the contact spacing between the source and drain. The measurement results of the I-V characteristics are calibrated and investigated by TCAD Atlas-Silvaco. The self-heating simulations show a hotspot at the vicinity of the drain side. The electrical stress that is applied on the Ohmic contacts decreases the polarisation as the source-drain distance is reduced, causing the inverse piezoelectric effect.

Thin film crystalline silicon (c-Si) solar cells have been a hot topic of photovoltaic research recently because its lower material consumption could potentially lead to lower capital expenditure. However, contact recombination is more prominent in thin-film c-Si solar cells compared with it in traditional c-Si solar cells due to higher carrier concentration. To address such a challenge, this work presents a design of metal-insulator-semiconductor (MIS) contact, based on thin TiOx layer that is grown by atomic layer deposition (ALD). Transmission line measurement (TLM) was conducted to study the conducting behavior of the TiOx MIS contact structure. Experimental results demonstrate that with the same doping density in silicon, the TiOx MIS contact forms an Ohmic contact to n-type silicon with good conductivity while cannot form Ohmic contact with p-silicon. This result demonstrates that the ALD TiOx layer can conduct electrons while blocking holes, thereby potentially reduce the contact recombination for thin-film c-Si solar cells, leading to an improvement of cell efficiency.

Fast and selective inductive heating of pre-sintered silver lines on silicon as present in solar cells using 27 MHz radio-frequency inductive fields is shown. IR measurements of silicon substrates show that above 450 °C the heating rate of the samples increases sharply, indicating that both the silver and the silicon are heated. By moving the substrate with respect to the RF antenna and modulation of the RF field, silicon wafers were heated reproducibly above 450 °C with heating rates in excess of 200 °C s-1. Furthermore, selective heating of lines of pre-sintered silver paste was shown below the 450 °C threshold on silicon substrates. The orientation of the silver tracks relative to the RF antenna appeared to be crucial for homogeneity of heating. Transmission line measurements show a clear effect on contact formation between the silver lines and the silicon substrate. To lower the contact resistance sufficiently for industrial feasibility, a high temperature difference between the Si substrate and the Ag tracks is required. The present RF heating process does not match the time scale needed for contact formation between silver and silicon sufficiently, but the significantly improved process control achieved shows promise for applications requiring fast heating and cooling rates.

A conducting polymer, poly 3-hexylthiophene (P3HT) is characterized with the metal-insulator-semiconductor (MIS) measurement method and the high frequency planar circuit method. From the MIS measurement method, the relative dielectric constant of the P3HT film is estimated to be 4.4. For the high frequency planar circuit method, a coplanar waveguide is fabricated on the P3HT film. When applying +20 V to the CPW on P3HT film, the P3HT film is in accumulation mode and becomes lossy. The CPW on P3HT film is 1.5 dB lossier than the CPW on film without P3HT film at 50 GHz.

The electrical performances of Pt/TiO(2)/Ti/Pt stacked Schottky-type diode (SD) was systematically examined, and this performance is dependent on the chemical structures of the each layer and their interfaces. The Ti layers containing a tolerable amount of oxygen showed metallic electrical conduction characteristics, which was confirmed by sheet resistance measurement with elevating the temperature, transmission line measurement (TLM), and Auger electron spectroscopy (AES) analysis. However, the chemical structure of SD stack and resulting electrical properties were crucially affected by the dissolved oxygen concentration in the Ti layers. The lower oxidation potential of the Ti layer with initially higher oxygen concentration suppressed the oxygen deficiency of the overlying TiO(2) layer induced by consumption of the oxygen from TiO(2) layer. This structure results in the lower reverse current of SDs without significant degradation of forward-state current. Conductive atomic force microscopy (CAFM) analysis showed the current conduction through the local conduction paths in the presented SDs, which guarantees a sufficient forward-current density as a selection device for highly integrated crossbar array resistive memory.

The effect of low-temperature (200 °C) annealing on the threshold voltage, carrier density, and interface defect density of amorphous indium zinc oxide (a-IZO) thin film transistors (TFTs) is reported. Transmission electron microscopy and x-ray diffraction analysis show that the amorphous structure is retained after 1 h at 200 °C. The TFTs fabricated from as-deposited IZO operate in the depletion mode with on–off ratio of > 106, sub-threshold slope (S) of ~ 1.5 V/decade, field effect mobility (μFE) of 18 ± 1.6 cm2/Vs, and threshold voltage (VTh) of − 3 ± 0.7 V. Low-temperature annealing at 200 °C in air improves the on-current, decreases the sub-threshold slope (1.56 vs. 1.18 V/decade), and increases the field effect mobility (μFE) from 18.2 to 23.3 cm2/Vs but also results in a VTh shift of − 15 ± 1.1 V. The carrier density in the channel of the as-deposited (4.3 × 1016 /cm3) and annealed at 200 °C (8.1 × 1017 /cm3) devices were estimated from test-TFT structures using the transmission line measurement methods to find channel resistivity at zero gate voltage and the TFT structures to estimate carrier mobility.

The demands on dielectric material measurements have increased over the years as electrical components have been miniaturized and device frequency bands have increased. Well-characterized dielectric measurements on thin materials are needed for circuit design, minimization of crosstalk, and characterization of signal-propagation speed. Bulk material applications have also increased. For accurate dielectric measurements, each measurement band and material geometry requires specific fixtures. Engineers and researchers must carefully match their material system and uncertainty requirements to the best available measurement system. Broadband measurements require transmission-line methods, and accurate measurements on low-loss materials are performed in resonators. The development of the most accurate methods for each application requires accurate fixture selection in terms of field geometry, accurate field models, and precise measurement apparatus.

AlGaN/GaN High Electron Mobility Transistors have been realized on resistive Si(111)/SiO2/polySiC substrates. The epitaxial structures were grown by Molecular Beam Epitaxy. The structural, optical, and electrical properties of these films are studied and compared with those of reference heterostructures grown on thick Si(111) substrates. Channel mobility of 1470 cm2/Vs at room temperature and sheet carrier density of 6.65x1012 cm–2 have been achieved. Field effect transistors with 3.6 µm x 100 µm gates have been fabricated on these layers and exhibit a drain current superior to 450 mA/mm and a transconductance of 123 mS/mm. Furthermore, to evaluate the influence of heat transfer onto electrical properties, the resistance change with the power dissipated inside Transmission Line Measurement devices has been compared with those in devices realized with layers grown on thick Si(111) and 4H-SiC substrates. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Extraction of the specific contact resistance, ρc, using the established circular transmission line measurement (c-TLM) and a series resistance measurement across mesa-isolated diodes is compared for a non-alloyed Pd/Ag contact to p-GaN. The limitations of the c-TLM technique are discussed and it is shown that for ρc values below 10−4 Ω cm2 both unintentional submicron errors in the actual radii and uncertainty in the resistance measurements can lead to order of magnitude changes in the extracted ρc. An additional current–voltage measurement across a mesa-isolated diode is proposed. The accuracy of the extracted ρc in this case requires consistency of the intrinsic diode characteristic, namely the ideality, at the bias voltages used for extraction, which is in turn related to the carrier transport and recombination properties. From a comparison with the c-TLM, we conclude that the resistance should be extracted at current densities

The requirements for dielectric measurements on polar liquids lie largely in two areas. First there is scientific interest in revealing the structure of and interactions between the molecules - this can be studied through dielectric spectroscopy. Secondly, polar liquids are widely used as dielectric reference and tissue equivalent materials for biomedical studies and for mobile telecommunications, health and safety related measurements. This review discusses these roles for polar liquids and surveys the techniques available for the measurement of their complex permittivity at RF and Microwave frequencies. One aim of the review is to guide researchers and metrologists in the choice of measurement methods and in their optimization. Particular emphasis is placed on the importance of traceability in these measurements to international standards

In this study, Ohmic contact were fabricated on AlGaAs HEMTs structure. A good metal-semiconductor interface are essentially for achieving lower specific contact resistance. An AlGaAs epi wafer was supply by the vendor. AlGaAs substrate was cleaned using wet chemical etching. Electrodes were fabricated through a sequenced of lithography, cleaning, sputtering and lift-off processes. The electrodes were made with metal layers of Ge, Au and Ni. Parameters such as metal thickness, annealing temperatures (from 300°C to 400°C) and annealing time were varies during fabrication process. Electrical characterizations after annealing are carried out using transmission line method (TLM) to obtain the specific contact resistance. Annealing temperature between 340°C to 360°C produced contact resistance below 5 x 10ˉ³Ω/cm-2.