Doping Of Transistors Research Articles

Reversible and Precisely Controllable p/n-Type Doping of MoTe2 Transistors through Electrothermal Doping.

Precisely controllable and reversible p/n-type electronic doping of molybdenum ditelluride (MoTe2 ) transistors is achieved by electrothermal doping (E-doping) processes. E-doping includes electrothermal annealing induced by an electric field in a vacuum chamber, which results in electron (n-type) doping and exposure to air, which induces hole (p-type) doping. The doping arises from the interaction between oxygen molecules or water vapor and defects of tellurium at the MoTe2 surface, and allows the accurate manipulation of p/n-type electrical doping of MoTe2 transistors. Because no dopant or special gas is used in the E-doping processes of MoTe2 , E-doping is a simple and efficient method. Moreover, through exact manipulation of p/n-type doping of MoTe2 transistors, quasi-complementary metal oxide semiconductor adaptive logic circuits, such as an inverter, not or gate, and not and gate, are successfully fabricated. The simple method, E-doping, adopted in obtaining p/n-type doping of MoTe2 transistors undoubtedly has provided an approach to create the electronic devices with desired performance.

Special Issue Dedicated to Prof. Daoben Zhu's 75th Birthday

First of all, I, together with my colleagues and friends, would like to send our best wishes to Professor Daoben Zhu on the occasion of his 75th birthday. Professor Zhu began his chemistry studies at East China University of Science and Technology (ECUST) in 1965 and graduated in 1968. He then joined the Institute of Chemistry, Chinese Academy of Sciences as an assistant professor, and was promoted to associate professor in 1985 and professor at 1987. He was a visiting scholar at the Max-Planck Institute for Medical Research in Heidelberg, Germany, from 1977 to 1979. He again worked as a visiting scientist at the same Max-Planck Institute in 1985 and 1986. Professor Zhu is one of the pioneers in the area of molecular materials and devices in China. He has been the director of the CAS Key Laboratory of Organic Solids since its establishment. He and his co-workers have made remarkable contributions to interdisciplinary cutting-edge research areas including organic conductors and superconductors, functional Langmuir–Blodgett films, fullerene chemistry and physics, light-emitting materials and devices, organic semiconductors and devices, and organic thermoelectronic materials and devices. These research achievements have provided in-depth understanding of the electronic processes and related phenomena in organic solids, thus boosting research into molecular materials and devices. Professor Zhu has published two books and more than 1000 papers in scientific journals, which have received more than 24 000 citations, and has an H-index of 90. His research accomplishments have been well recognized by the scientific community. He has received National Natural Sciences of China second-class prizes five times, in 1988, 2002, 2004, 2007 and 2014. He was the winner of the Chinese Chemical Society—the China Petroleum and Chemical Corporation Chemical Contribution Award in 2008, and he won the Tan Kah Kee Science Award in chemistry in 2012. Professor Zhu was elected as a Chinese Academy of Sciences Academician in 1997 and a member of the World Academy of Sciences for the advancement of science in developing countries in 2009. In 2014 and 2015, Professor Zhu was selected by Thomson Reuters as one of the world's most influential scientific minds both in chemistry and materials science. Apart from doing scientific research, Professor Zhu has made great contributions to the administration and management of scientific research in China. Among the administration positions he has held, he was the director of the Institute of Chemistry, Chinese Academy of Sciences from 1992 to 2000, vice president of the National Natural Science Foundation of China from 2000 to 2007, president of the Chinese Chemical Society from 1994 to 1997, and vice president of the Chinese Materials Society from 2001 to 2005. He was the vice chairman of the second, fourth and fifth advisory committees of the National Basic Research Program of China (973 Program). He is now the vice chairman of the Academic Committee of Chinese Academy of Sciences (CAS) and the committee chair of the Academic Division of Chemistry, CAS. Professor Zhu has continuously supported and actively promoted scientific exchanges and collaborations between Chinese scientists and leading scientists across the world. We publish this special issue to celebrate the 75th birthday of Professor Zhu and express sincere thanks to him for his continuous support over many years. This special issue collects research communications, full research papers, and reviews that cover the following topics: organic semiconductors, doping of organic semiconductors and field-effect transistors, graphdiyne and carbon ene-yne nanoribbon, photovoltaic cells and photodetectors, bioelectronics, and organic nonlinear optical materials. We would like to take this opportunity to thank the distinguished authors who contributed to this special issue, and the editorial staff of Advanced Electronic Materials for enabling its publication. Professor Yuliang Li has worked at the Institute of Chemistry, Chinese Academy of Sciences since 1975. He was a visiting scholar in the Department of Chemistry at University of Amsterdam (The Netherlands) from 1987 to 1989, was a visiting professor at the Radiation Lab at University of Notre Dame (USA) from August 1998 to March 1999, and worked in the Department of Chemistry at the University of Hong Kong from September 1999 to February 2000. His research interests include the growth of low-dimensional and two-dimensional carbon nanostructures, covalently and non-covalently assembled molecular materials, and supramolecular chemistry.

Molecular doping of MoS2 transistors by self-assembled oleylamine networks

Thin MoS2 films continue to be of key interest for numerous applications; however, effective doping and high metal to MoS2 contact resistance are challenges for future applications. We report on the self-assembly of oleylamine on top of MoS2 thin-films and the effective doping of MoS2 thin-film field effect transistors by oleylamine. Atomic force microscopy revealed that oleylamine organizes in lamellae domains on MoS2 thin films with similar characteristics of those previously observed on highly ordered pyrolytic graphite. A carrier concentration increase from 7.1 × 1011 cm−2 up to 1.9 × 1013 cm−2 at 0 V gate voltage is achieved together with a reduction of the contact resistance by a factor of 5 when using gold as metal contact. Furthermore, this non-covalent doping proves to be removable and reproducible among different flakes and does not degrade the electron mobility. Thus, this work opens the path for future works on controlling the doping of MoS2 by proper selection of the self-assembled species.

Influence of self-assembled monolayer binding group on graphene transistors

Graphene transistors on self-assembled monolayer (SAM) modified dielectric substrates were fabricated and characterized in order to determine the influence SAM binding group has on device properties. It was found that silane based alkyl SAMs had little to no influence in doping graphene transistors, while phosphonic acid based ones caused n-type doping of graphene transistors with a charge neutrality point shift of over 10 V. It was also discovered that alkyl SAM packing density influenced the doping magnitude. Due to substrate surface charge trap quenching, these SAMs independent of binding group enhanced charge mobility of graphene transistors compared to ones on bare oxide substrates.

A simple method for controllable solution doping of complete polymer field-effect transistors

Controllable p-type doping of both poly(3-hexylthiophene) (P3HT) and poly(triarylamine) (PTAA) organic field effect transistors (OFETs) was achieved by immersing complete top-contact OFETs in a solution of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) in acetone. As this method is applied to complete devices, it has a greater utility than methods involving doping of the solution prior to film deposition as it allows separation of the device processing and doping steps, facilitating the use of optimal processing conditions at each stage. It was found that by varying immersion time and the concentration of the dopant solution, it was possible to vary the threshold voltage for a P3HT OFET by over 30 V. Although PTAA devices are less sensitive to oxidation by F4-TCNQ than OFETs using P3HT, they can also be controllably doped by this method up to a threshold voltage of +12 V.

Dual n-type doped reduced graphene oxide field effect transistors controlled by semiconductor nanocrystals

Here, we demonstrate a rapid and simple method for doping a reduced graphene oxide (rGO) field effect transistor (FET) with nanocrystals to produce dual n-type behavior with light and bias voltage. This convenient method promises industrial level doping of graphene transistors.

Proton radiation response mechanisms in bipolar analog circuits

The experimental data presented in this paper indicate that the doping and geometry of critical transistors are the primary factors that affect the proton responses of the LM124 and LM148 operational amplifiers. The data also reveal that the electrical responses of these circuits and their input transistors to the combined effects of displacement damage and defects introduced by ionizing radiation are nonlinear. Analysis, supported by device simulation, shows that shifts in device parameters (surface potentials, carrier concentrations, etc.) caused by the buildup of oxide and interfacial defects affect the recombination rate due to traps resulting from displacement damage in the bulk silicon. This nonlinearity complicates the analysis of proton radiation effects and can have a significant impact on the qualification of analog parts for use in space environments.

Laser Processing of Polysilicon Thin-Film Transistors: Grain Growth and Device Fabrication

Pulsed excimer-laser processing of amorphous silicon on non-crystalline substrates is an important processing technology for large-area polysilicon electronics, such as flat-panel displays and two-dimensional imaging arrays. It also allows for the integration of amorphous silicon and polysilicon devices on the same glass substrate and provides procedures for the doping of self-aligned thin-film transistors. Materials studies show that laser-crystallized polysilicon exhibits a narrow peak in the average grain size as a function of the excimer laser energy density, with a corresponding peak in the electron mobility. This is of particular significance for devices since large grains imply high electron mobility. On the other hand, the peak in the grain size is very narrow and is also accompanied by a peak in the surface roughness of the film. These relationships force a compromise between large grain size for high mobility and homogeneous size distribution for uniformity of device characteristics. A window exists in process parameter space where good-quality devices with uniform characteristics have been obtained. Also, laser-processing enhancements, such as laser doping and fabrication of self-aligned transistors, provide additional tools to fabricate unique devices.

Characterization of AlGaAs/GaAs Heterojunction Bipolar Transistors Using Photoreflectance and Spectral Ellipsometry

AbstractPhotoreflectance spectroscopy (PR) and spectral ellipsometry (SE) have been used to characterize the doping and structure of heterojunction bipolar transistors (HBT). This information provides a more complete description of the epitaxial HBT structure than is possible by relying solely on electrical characterization of specially processed test structures. Additional benefit is derived from the nondestructive nature of both SE and PR. The measurements are fast enough to be implemented on all production-bound HBT material. We describe our recent results comparing capacitance-voltage measurements with PRderived doping levels in the emitter layer of the HBT. We also describe some work comparing SE fit results with Auger electron spectroscopy depth profiles for InGaAs contact layer composition and thickness.