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Search Publications by: David Gundlach (Fed)

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Displaying 1 - 25 of 88

The role of orientation in the MEL response of OLEDs

July 13, 2021
Sebastian Engmann, Emily Bittle, Lee J. Richter, Rawad Hallani, John Anthony, David J. Gundlach
Magneto electroluminescence (MEL) is emerging as a powerful tool for the study of spin dynamics in emitting devices. The shape of the MEL response is typically used to draw qualitative inference on the dominant process (singlet fission or triplet fusion)

High-density polyethylene - an inert additive with stabilizing effects on organic field-effect transistors

September 11, 2020
Alberto Scaccabarozzi, James Basham, Liyang Yu, Paul Westcott, Weimin Zhang, Aram Amassian, Iain McCulloch, Mario Caironi, David J. Gundlach, Natalie Stingelin
Organic electronics technologies have attracted considerable interest over the last decades and have become promising alternatives to conventional, inorganic platforms for specific applications. To fully exploit the touted potential of plastic electronics

Contact resistance in organic field-effect transistors: conquering the barrier

May 15, 2020
Matthew Waldrip, Oana Jurchescu, David J. Gundlach, Emily Bittle
Organic semiconductors have sparked significant interest due to their inherent properties as flexible, solution processible, and chemically tunable electronic materials. In the last 10 years, the improvements in charge carrier mobility in small molecule

Correlating anisotropic mobility and intermolecular phonons in organic semiconductors to investigate transient localization

March 19, 2019
Emily G. Bittle, Adam J. Biacchi, Lisa A. Fredin, Andrew A. Herzing, Thomas C. Allison, Angela R. Hight Walker, David J. Gundlach
Charge transport in organic semiconductors is governed by a mix of polaron hopping and band- like transport mechanisms. The energy of polaron hopping and formation are similar in magnitude to the energies of inter- and intra- molecular modes, which points

Higher Order Effects in Organic LEDs with Sub-bandgap Turn-on

January 16, 2019
Sebastian Engmann, Adam J. Barito, Emily Bittle, Chris Giebink, Lee J. Richter, David J. Gundlach
Spin-dependent nonlinear processes in organic materials such as singlet-fission and triplet- triplet annihilation could increase the performance for photovoltaics, detectors, and light emitting diodes. Rubrene/C60 light emitting diodes exhibit a distinct

Electrical Detection of Singlet Fission in Single Crystal Tetracene Transistors

January 4, 2019
Hyuk-Jae Jang, Emily Bittle, Qin Zhang, Adam Biacchi, Curt A. Richter, David J. Gundlach
Here, we present the electrical detection of singlet fission in tetracene by using a field- effect transistor (FET). Singlet fission is a photo-induced spin-dependent process yielding two triplet excitons from the absorption of a single photon. , In this

Band offset and electron affinity of MBE-grown SnSe2

January 25, 2018
Qin Zhang, Mingda Li, Edward Lochocki, Suresh Vishwanath, Xinyu Liu, Rusen Yan, Huai-Hsun Lien, Malgorzata Dobrowolska, Jacek Furdyna, Kyle M. Shen, Guangjun Cheng, Angela R. Hight Walker, David J. Gundlach, Huili G. Xing, Nhan V. Nguyen
SnSe2 is currently considered a potential 2D material that can form a near-broken gap heterojunction in a tunnel field-effect transistor (TFET) due to its conceivable large electron affinity, which is experimentally confirmed in this letter. With the

Calibration and impact of bulk trap-assisted tunneling and Shockley-Read-Hall currents in InGaAs tunnel-FETs

September 1, 2017
Quentin Smets, Anne S. Verhulst, Eddy Simoen, David J. Gundlach, Curt A. Richter, Nadine Collaert, Marc Heyns
The tunnel-FET (TFET) is a promising candidate for future low-power logic applications because it enables a sub-60 mV/dec subthreshold swing. However, most experimental TFETs are plagued by unwanted trap-assisted tunneling (TAT) and Shockley-Read-Hall (SRH

The dependence of electrical performance on structural organization in low mobility polymer field effect transistors

April 16, 2017
Emily G. Bittle, Hyun W. Ro, Chad R. Snyder, Sebastian Engmann, Regis J. Kline, Oana Jurchescu, Dean M. DeLongchamp, David J. Gundlach
Polymer semiconductors are contenders for use in printed, flexible electronics. Though organic electronic materials have been studied for many years, the physics of charge transport is still under investigation. This is in part due to the large variability

Cryogenic pulsed I-V measurements on homo- and heterojunction III-V TFETs

April 1, 2017
Quentin Smets, Jihong Kim, Jason Campbell, David M. Nminibapiel, Dmitry Veksler, Pragya Shrestha, Rahul Pandey, Anne S. Verhulst, Eddy Simoens, David J. Gundlach, Curt A. Richter, Kin P. Cheung, Suman Suman, Anda Mocuta, Nadine Collaert, Aaron Thean, Marc Heyns
Most experimental reports of tunneling field-effect transistors show defect-related performance degradation. Charging of oxide traps causes Fermi level pinning, and Shockley-Read-Hall (SRH)/trap-assisted tunneling (TAT) generation cause unwanted leakage

Reduced Bimolecular Recombination in Blade-Coated, High-Efficiency, Small-Molecule Solar Cells

March 22, 2017
Sebastian Engmann, Hyun W. Ro, Andrew A. Herzing, Dean M. DeLongchamp, Chad R. Snyder, Lee J. Richter, Adam J. Barito, David J. Gundlach
The full benefit of emerging solution deposited photovoltaic devices requires development of processes compatible with high speed manufacturing. Extensive studies of the lab-to-fab challenge have been performed on polymer donor based organic photovoltaics

Calibration of Effective Tunneling Bandgap in GaAsSb/InGaAs for improved TFET Performance Prediction

November 3, 2016
Quentin Smets, Anne S. Verhulst, Salim El Kazzi, David J. Gundlach, Curt A. Richter, Anda Mocuta, Nadine Collaert, Aaron Thean, Marc Heyns
The effective bandgap for heterojunction band-to-band tunneling (Eg,eff) is a crucial design parameter for heterojunction TFET. However, there is significant uncertainty on Eg,eff, especially for In0.53Ga0.47As/GaAs0.5Sb0.5. This makes TFET performance

Observation of Strong Reflection of Electron Waves Exiting a Ballistic Channel at Low Energy

June 10, 2016
Jason Campbell, Jason Ryan, Kin P. Cheung, David J. Gundlach, Changze Liu, Canute I. Vaz, Richard G. Southwick III, Anthony S. Oates, Ru Huang
Wave scattering by a potential step is a nearly ubiquitous concept. Thus, it is surprising that theoretical treatments of ballistic transport in nanoscale devices, from quantum point contacts to ballistic transistors, assume no reflection even when the

Mobility overestimation due to gated contacts in organic field-effect transistors

March 10, 2016
Emily G. Bittle, David J. Gundlach, Oana Jurchescu, James I. Basham, Thomas Jackson
Parameters used to describe the electrical properties of organic field-effect transistors, such as mobility and threshold voltage, are commonly extracted from measured current–voltage characteristics and interpreted by using the classical metal oxide

Broadband Optical Properties of Graphene by Spectroscopic Ellipsometry

December 11, 2015
Wei Li, Nhan Van Nguyen, Guangjun Cheng, Angela R. Hight Walker, David J. Gundlach, Yiran Liang, boyuan Tian, Xuelei Liang, Lian-Mao Peng
The broadband (0.7 eV to 9.0 eV) optical properties of chemical-vapor-deposition (CVD) grown graphene are determined by spectroscopic ellipsometry. The optical absorption follows the fine structure constant in the energy range from 1.0 eV to 2.0 eV, but

Influence of Metal?MoS2 Interface on MoS2 Transistor Performance: Comparison of Ag and Ti Contacts

December 16, 2014
Hui H. Yuan, Guangjun Cheng, Lin You, Haitao Li, Hao Zhu, Wei Li, Joseph J. Kopanski, Yaw S. Obeng, Angela R. Hight Walker, David J. Gundlach, Curt A. Richter, D. E. Ioannou, Qiliang Li
In this work, we present a study of enhancing MoS2 transistor performance by using proper metal contact. We found that the on-state current of MoS2 field-effect transistors with 30 nm Au/ 30 nm Ag contacts is enhanced more than 60 times and the

Electron and Hole Photoemission Detection for Band Offset Determination of Tunnel Field-Effect Transistor Heterojunctions

November 24, 2014
Wei Li, Qin Zhang, R. Bijesh, Oleg A. Kirillov, Yiran Liang, Igor Levin, Lianmao Peng, Xuelei Liang, S. Datta, David J. Gundlach, Nhan V. Nguyen
The electrical performance of a tunnel field-effect transistor depends critically on the band offset at their semiconductor heterojunction interface. Historically, it has been difficult to experimentally determine how the electronic bands align at the