A diode is a widely used electronic device that acts as a one-way switch for electric current. A well-known example is the LED (Light Emitting Diode), but there is a special class of diode designed to take advantage of a phenomenon called “quantum tunneling”. Called Resonant Tunnel Diodes (RTDs), these devices are one of the fastest semiconductor devices used in countless practical applications such as terahertz band radio frequency oscillators, wave emitters, wave detectors, and logic gates. It has been. Example. RTDs are also light sensitive and can be used as photoactive elements in photodetectors or optoelectronic circuits.
Quantum tunneling (or tunneling effect) is a phenomenon described by quantum mechanics that allows particles to transition through classically forbidden energy states. In other words, even if the kinetic energy is lower than the potential energy of the potential barrier, it is possible to escape from the area surrounded by the potential barrier.
“RTDs consist of two potential barriers separated by layers that form quantum wells. This structure is formed by a highly charged semiconductor alloy that accelerates when a voltage is applied to the RTD. It is sandwiched between the alloyed tips. It occurs when the energy of the charge accelerated by the application of the tunnel effect voltage matches the quantized energy level of the quantum well. When the voltage is applied, the barrier The energy of the electrons held by them increases and, at certain levels, can cross the forbidden region, but when higher voltages are applied, the energy of the electrons becomes the quantized energy in the well. “Because of the above, electrons cannot pass through,” said Marcio Dardin Theodoro, a professor of federal physics. University of San Carlos (UFSCar) in the state of Sao Paulo, Brazil.
Teodoro was the lead investigator in the study of determining RTD charge accumulation and dynamics over the applied voltage range. A paper explaining this study has been published in Physical Review Applied. This study was supported by FAPESP through four projects (13/18719-1, 14/1914-2, 14/02112-3, and 18/01914-0).
“The behavior of RTD-based devices depends on several parameters, such as charge excitation, storage, transport, and the relationships between these properties,” says Teodoro. “The charge carrier densities of these devices are always determined before and after the resonance region, but not in the resonance region itself, which conveys important information. Using advanced spectroscopy and electron transport technology. , Determined the charge accumulation and dynamics of the entire device. The characteristic of tunneling is a sharp drop to a specific voltage that depends on the peak current and the subsequent structural characteristics of the RTD. “
magnetic field
Previous studies have measured charge carrier densities as a function of voltage using magnetic transport techniques that correlate current intensity with magnetic fields. However, magnetic transport tools may not be able to characterize charge accumulation over the entire operating range, and there may be blind spots at certain voltage values. As a result, researchers also used a technique called magnetic electroluminescence to investigate the luminescence induced by the applied voltage as a function of the magnetic field.
“Magnetic electroluminescence allowed us to study the voltage band, which is the blind spot for magnetic transport. The results were consistent at the point where both methods could measure charge density,” said Edson, the lead author of the paper. Rafael Cardozode Oliveira says. “These two experimental techniques have proven to complement a complete study of charge density across the RTD’s operating voltage range.”
Cardozo de Oliveira has a PhD. After earning a PhD in Sandwich from Germany from the Faculty of Technical Physics at the University of Würzburg, he majored in Physics with Theodoro as a dissertation advisor. Among his other contributions to the research was writing software used to process vast amounts of data on the order of gigabytes generated by experiments.
“This study could lead to further research on RTDs, which could lead to the production of more efficient optoelectronic devices,” he said. “By monitoring charge accumulation as a function of voltage, it is possible to develop new RTDs with an optimized charge distribution to improve photodetection efficiency and minimize light loss. Become.”
Since RTDs are very complex structures, it is important to know how the charges are distributed in the RTDs. Victor Lopez Richard, a UFSCar professor and co-author of the treatise, said:
Paper “Determination of Carrier Density and Dynamics by Magnetic Electroluminescence Spectroscopy in Resonant Tunnel Diodes”
Researchers have realized a resonant tunneling diode based on the twisted black phosphorus homostructure.
For more information:
ER Cardozo de Oliveira et al, Determining Carrier Density and Dynamics by Magnetic Electroluminescence Spectroscopy of Resonant Tunnel Diodes, Physical review applied (2021). DOI: 10.1103 / PhysRevApplied.15.014042
Quote: According to research, more efficient optoelectronic devices obtained on April 20, 2021 from https: //phys.org/news/2021-04-production-efficient-optoelectronic-devices.html (April 20, 2021) May lead to production
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Research may lead to the production of more efficient optoelectronic devices
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