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Towards High Solar Cell Efficiency with Low Material Usage: 15% Efficiency with 14 ?μm Polycrystalline Silicon on Glass
摘要： This work showcases a bottom-up approach to creating silicon solar cells using a line-shaped laser. We report efforts to create thicker amorphous silicon passivation and contact layers as well as laser firing for low contact resistance. Collectively, a new in-house record efficiency of 15.1 % was achieved along with a clear pathway to reach 16 % efficiency with optimization of series resistance.
关键词： Foreign substrates,Liquid phase crystallized silicon,Passivation,Silicon Heterojunction Interdigitated back contact,Laser fired contacts
更新于2025-11-14 15:25:21
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Temperature-Dependent Electrical Characteristics of β-Ga <sub/>2</sub> O <sub/>3</sub> Diodes with W Schottky Contacts up to 500°C
摘要： The development of thermally stable contacts capable of high temperature operation are necessary for Ga2O3 high power rectifiers. We have measured the electrical characteristics of sputter-deposited W Schottky contacts with Au overlayers for reducing sheet resistance on n-type Ga2O3 before and after device operation up to 500°C. Assuming thermionic emission is dominant, the extracted barrier height decreases with measurement temperature from 0.97 eV (25°C) to 0.39 eV (500°C) while showing little change from its initial value of 0.97 eV after cooling down from each respective operation temperature. The room temperature value is comparable to that obtained by determining the energy difference between binding energy of the Ga 3d core level and the valence band of the Ga2O3 when W is present, 0.80 ± 0.2 eV in this case. The Richardson constant was 54.05 A.cm?2.K?2 for W and the effective Schottky barrier height at zero bias (eφb0) was 0.92 eV from temperature-dependent current-voltage characteristics. The temperature coefficient for reverse breakdown voltage was 0.16 V/K for W/Au and 0.12 V/K for Ni/Au. The W-based contacts are more thermally stable than conventional Ni-based Schottkies on Ga2O3 but do show evidence of Ga migration through the contact after 500°C device operation.
关键词： electrical characteristics,thermal stability,high temperature operation,Ga2O3,Schottky contacts
更新于2025-09-23 15:23:52
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Switchable Schottky contacts: Simultaneously enhanced output current and reduced leakage current
摘要： Metal-semiconductor contacts are key components of nanoelectronics and atomic-scale integrated circuits. In these components Schottky diodes provide a low forward voltage and a very fast switching rate but suffer the drawback of a high reverse leakage current. Improvement of the reverse bias characteristics without degrading performance of the diode at positive voltages is deemed physically impossible for conventional silicon-based Schottky diodes. However, in this work we propose that this design challenge can be overcome in the organic-based diodes by utilizing reversible transitions between distinct adsorption states of organic molecules on metal surfaces. Motivated by previous experimental observations of controllable adsorption conformations of anthradithiophene on Cu(111), herein we use density functional theory simulations to demonstrate the distinct Schottky barrier heights of the two adsorption states. The higher Schottky barrier of the reverse bias induced by chemisorbed state results in low leakage current; while the lower barrier of the forward bias induced by physisorbed state yields a larger output current. The rectifying behaviors are further supported by nonequilibrium Green's function transport calculations.
关键词： van der Waals forces,Schottky contacts,Schottky barrier height,reverse leakage current,bistable state
更新于2025-09-23 15:23:52
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Accurate Graphene-Metal Junction Characterization
摘要： A reliable method is proposed for measuring specific contact resistivity (ρC) for graphene-metal contacts, which is based on a contact end resistance measurement. We investigate the proposed method with simulations and confirm that the sheet resistance under the metal contact (RSK) plays an important role, as it influences the potential barrier at the graphene-metal junction. Two different complementary metal-oxide-semiconductor-compatible aluminum-based contacts are investigated to demonstrate the importance of the sheet resistance under the metal contact: the difference in RSK arises from the formation of insulating aluminum oxide (Al2O3) and aluminum carbide (Al4C3) interfacial layers, which depends on the graphene pretreatment and process conditions. Auger and X-Ray photoelectron spectroscopy (XPS) support electrical data. The method allows direct measurements of contact parameters with one contact pair and enables small test structures. It is further more reliable than the conventional transfer length method (TLM) when the sheet resistance of the material under the contact is large. The proposed method is thus ideal for geometrically small contacts where it minimizes measurement errors and it can be applied in particular to study emerging devices and materials.
关键词： TLM,graphene,electrical contacts
更新于2025-09-23 15:22:29
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Contact Engineering for Dual-Gate MoS <sub/>2</sub> Transistors Using O <sub/>2</sub> Plasma Exposure
摘要： The benefits of O2 plasma exposure at the contact regions of dual-gate MoS2 transistors prior to metal deposition for high performance electron contacts is studied and evaluated. Comparisons between devices with and without the exposure demonstrate significant improvements due to the formation of a high-quality contact interface with low electron Schottky barrier (~0.1 eV). Topographical and interfacial characterization are used to study the contact formation on MoS2 from the initial exfoliated surface through the photolithography process and Ti deposition. Fermi level pinning near the conduction band is shown to take place after photoresist development leaves residue on the MoS2 surface. After O2 plasma exposure and subsequent Ti deposition, Ti scavenges oxygen from MoOx and forms TiOx. Electrical characterization results indicate that photoresist residue and other contaminants present after development can significantly impact electrical performance. Without O2 plasma exposure at the contacts, output characteristics of MoS2 FETs demonstrate non-linear, Schottky-like contact behavior compared to the linearity observed for contacts with exposure. O2 plasma allows for the removal of the residue present at the surface of MoS2 without the use of a high temperature anneal. A low conduction band offset and superior carrier injection are engineered by employing the reactive metal Ti as the contact to deliberately form TiO2. Dual-gate MoS2 transistors with O2 plasma exposure at the contacts demonstrate linear output characteristics, lower contact resistance (~20× reduction), and higher field effect mobility (~15× increase) compared to those without the treatment. In addition, these results indicate that device fabrication process induced effects cannot be ignored during the formation of contacts on MoS2 and other 2D materials.
关键词： TiO2,MoS2,contact resistance,O2 plasma,photoresist residue,MOSFETs,contacts
更新于2025-09-23 15:22:29
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Recent Advances in β-Ga2O3–Metal Contacts
摘要： Ultra-wide bandgap beta-gallium oxide (β-Ga2O3) has been attracting considerable attention as a promising semiconductor material for next-generation power electronics. It possesses excellent material properties such as a wide bandgap of 4.6–4.9 eV, a high breakdown electric field of 8 MV/cm, and exceptional Baliga’s figure of merit (BFOM), along with superior chemical and thermal stability. These features suggest its great potential for future applications in power and optoelectronic devices. However, the critical issue of contacts between metal and Ga2O3 limits the performance of β-Ga2O3 devices. In this work, we have reviewed the advances on contacts of β-Ga2O3 MOSFETs. For improving contact properties, four main approaches are summarized and analyzed in details, including pre-treatment, post-treatment, multilayer metal electrode, and introducing an interlayer. By comparison, the latter two methods are being studied intensively and more favorable than the pre-treatment which would inevitably generate uncontrollable damages. Finally, conclusions and future perspectives for improving Ohmic contacts further are presented.
关键词： Intermediate semiconductor layer,Metal stacks,Contacts,β-Ga2O3
更新于2025-09-23 15:22:29
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26.1%-efficient POLO-IBC cells: Quantification of electrical and optical loss mechanisms
摘要： We present experimental results for interdigitated back contacted (IBC) solar cells with passivating POLO contacts for both polarities with a nominal intrinsic poly‐Si region between them. We reach efficiencies of 26.1% and 24.9% on a 1.3 Ω cm and 80 Ω cm p‐type FZ wafer and 24.6% on a 2 Ω cm n‐type Cz wafer, respectively. The initially measured implied efficiency potentials of the cells after passivating the surfaces are very similar, namely, 26.8%, 26.8%, and 26.4%, respectively. We attribute the difference between the efficiency potential and the final current‐voltage measurement to degradation, perimeter, and series and shunt resistance losses, which we quantify by lifetime measurements. With these measurements in combination with a finite element simulation, we determine the surface recombination velocity in the nominal intrinsic poly‐Si region to be in the range from 13 to 21 cm s?1. Using the same approach, we analyze the increase of the front surface recombination velocity during cell processing from 2 to 10 cm s?1 for the 1.3 Ω cm and from 0.5 to 2.3 cm s?1 for the 80 Ω cm. This leads to the fact that cells fabricated on lowly doped bulk material are more vulnerable to a process‐induced degradation of the surface passivation quality. We further determine the theoretical limits of the cells by firstly idealizing the recombination (28% for 1.3 Ω cm and 28.2% for 80 Ω cm) and secondly also idealizing the optics of the solar cells (29.4% and 29.5%).
关键词： IBC solar cells,efficiency potential,lifetime monitoring,POLO,passivating contacts
更新于2025-09-23 15:22:29
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1D ballistic transport channel probed by invasive and non-invasive contacts
摘要： Epitaxially grown sidewall graphene nanoribbons show a robust quantum conductance of e2/h. By means of in-situ transport measurements with a nanoprobe system, we realized invasive and non-invasive 4-point-probe configurations. The invasiveness correlates with the contact resistance of the voltage probes. In particular, we achieved now non-invasive voltage probes revealing an almost zero resistance in a collinear 4 point-probe measurement. This proofs the ballistic nature of our epitaxially grown sidewall nanoribbons on SiC(0001) mesa structures.
关键词： quantum conductance,graphene nanoribbons,ballistic transport,non-invasive contacts,invasive contacts
更新于2025-09-23 15:21:21
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Charge noise analysis of metal oxide semiconductor dual-gate Si/SiGe quantum point contacts
摘要： The frequency dependence of conductance noise through a gate-defined quantum point contact fabricated on a Si/SiGe modulation doped wafer is characterized. The 1/f2 noise, which is characteristic of random telegraph noise, is reduced by application of a negative bias on the global top gate to reduce the local gate voltage. Direct leakage from the large global gate voltage also causes random telegraph noise, and therefore, there is a suitable point to operate quantum dot measurement.
关键词： quantum point contacts,global top gate,charge noise,Si/SiGe,random telegraph noise
更新于2025-09-23 15:21:21
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Transparent Electronics Using One Binary Oxide for All Transistor Layers
摘要： A novel process is developed in which thin film transistors (TFTs) comprising one binary oxide for all transistor layers (gate, source/drain, semiconductor channel, and dielectric) are fabricated in a single deposition system at low temperature. By simply changing the flow ratio of two chemical precursors, C8H24HfN4 and (C2H5)2 Zn, in an atomic layer deposition system, the electronic properties of the binary oxide (HfxZn1?xO2?δ or HZO) are tuned from conducting, to semiconducting, to insulating. Furthermore, by carefully optimizing the properties of the various transistor HZO layers, all-HZO thin film transistors are achieved with excellent performance on both glass and plastic substrates. Specifically, the optimized all-HZO TFTs show a saturation mobility of ≈17.9 cm2 V?1 s?1, low subthreshold swing of ≈480 mV dec?1, high Ion/Ioff ratio of >109, and excellent gate bias stability at elevated temperatures. In addition, all-HZO inverters with high DC voltage gain (≈470), and all-HZO ring oscillators with low stage delay (≈408 ns) and high oscillation frequency of 245 kHz are demonstrated. This approach presents a novel, simple, high performance, and cost-effective process for the fabrication of indium-free transparent electronics.
关键词： transparent multilayer semiconducting channel,transparent electronics,transparent oxide contacts,thin film,transistors,transparent dielectric oxides
更新于2025-09-23 15:21:21