Navigation Links
Avalanche photodiodes target bioterrorism agents
Date:6/26/2008

Researchers have shown that a new class of ultraviolet photodiode could help meet the U.S. military's pressing requirement for compact, reliable and cost-effective sensors to detect anthrax and other bioterrorism agents in the air.

"The military is currently using photomultiplier tubes, which are bulky, fragile and require a lot of power to run them, or silicon photodiodes that require a complex filter so that they only detect the desired ultraviolet light," said Russell Dupuis, Steve W. Chaddick Endowed Chair in Electro-Optics in Georgia Tech's School of Electrical and Computer Engineering (ECE) and a Georgia Research Alliance Eminent Scholar.

New research shows that ultraviolet avalanche photodiodes offer the high gain, reliability and robustness needed to detect these agents and help authorities rapidly contain an incident like the 2001 anthrax attacks. The fabrication methods and device characteristics were described at the 50th Electronic Materials Conference in Santa Barbara on June 25. Details of the photodiodes were also published in the February 14 issue of the journal Electronics Letters and the November 2007 issue of the journal IEEE Photonics Technology Letters.

ECE associate professor Douglas Yoder, assistant professor Shyh-Chiang Shen and senior research engineer Jae-Hyun Ryou collaborated on this research, which is funded by the Defense Advanced Research Projects Agency (DARPA) and the Georgia Research Alliance.

The team chose to develop avalanche photodiodes for this bioterrorism application because the devices can detect the signature fluorescence of biological molecules in a sample of air. Since most of the molecules of interest to the researchers emit ultraviolet light, they designed special photodiodes that detect the fluorescence in the ultraviolet region, but have no response to visible light.

"We built our photodiodes with gallium nitride, which is a semiconductor that can be used to create photodiodes that require no filters because this material has an inherent response to ultraviolet, but no response to visible light or solar flux," explained Dupuis.

To improve the sensitivity at ultraviolet wavelengths, the researchers designed the gallium nitride photodiodes to operate in a mode that employs avalanche multiplication. The avalanche multiplication phenomenon is used to multiply normally tiny currents by factors of up to one million, thus dramatically increasing the device gain.

Avalanche photodiodes can create much larger currents for each photon compared to normal photodiodes. Once the necessary electric field strength has been achieved inside the device, the avalanche effect starts with just one free electron. Since the illuminated photodiode will contain many free electrons, an avalanche will always occur if the electric field is large enough.

"One electron-hole pair that is produced by a photon absorption event creates a million other electron-hole pairs and the current becomes a pulse of current that you can detect with special electronics," added Dupuis.

The researchers fabricated high-performance gallium nitride ultraviolet avalanche photodiodes on bulk gallium nitride substrates that demonstrate optical gains of 100,000 at ultraviolet wavelengths from 280 to 360 nanometers.

The gallium nitride device structures were grown by metalorganic chemical vapor deposition, a technique for depositing thin layers of atoms onto a semiconductor wafer. Many layers can be built up, each of a precisely controlled thickness and composition, to create a material which has specific optical and electrical properties. This is the first time gallium nitride was successfully used in the fabrication of photodiodes having ultraviolet optical gains greater than 10,000.

Since demonstrating the feasibility of the photodiodes to exhibit the avalanche effect, the research team has been developing a more advanced structure capable of operating as a Geiger-mode detector, so that the photodiodes are sensitive enough to detect only one photon at a time. When the Geiger-mode detector is connected to the avalanche circuitry, a single electron-hole pair can trigger a strong avalanche current to flow from just one photon.

Yoder, who works on Georgia Tech's Savannah, Ga. campus, is developing computer models of the new photodiodes to calculate the detailed electronic and optical transport. Yoder's goal is to optimize the materials and design of the Geiger-mode avalanche detector to assure optimal, reproducible performance of the avalanche photodiodes.

"Doug's work is pivotal because these applications don't require one working detector, they might require thousands of uniform detectors in the same chip that all function the same way, so our ability to manufacture identical photodiodes and detectors is important," said Dupuis.

With proper manufacturing, these avalanche photodiodes can be used for more than detecting bioterrorism agents. They can also be used detect fires, gun muzzle flashes, missile propulsion flames and maybe even cancer cells, according to Dupuis.


'/>"/>

Contact: Abby Vogel
avogel@gatech.edu
404-385-3364
Georgia Institute of Technology Research News
Source:Eurekalert  

Related biology technology :

1. Tiny avalanche photodiode detects single UV photons
2. In a Year of Unprecedented Growth for Biotechnology Innovation, Targeted Therapies Gain Most Significant Traction, According to New Deloitte Study
3. Realtime Achieves ISO 13485:2003 Certification Targeting BioTech Quality Initiative
4. onTargetjobs Announces Appointment of Michael Tansey as New CEO
5. Clarification on Press Release Issued Earlier Today: Targeted Genetics Confirms Positive, Interim Phase 1/2 Study Findings
6. ASCO 2008: Tumor-Targeted Rexin-G Demonstrates Dose-Dependent Anti-Tumor Activity Without Toxicity in Metastatic Pancreatic Cancer
7. Nektar Receives Patent Covering Pulmonary Targeted Antibiotics
8. New Study Raises Questions About Prostate Cancer Therapies Targeting Insulin-Like Growth Factor Receptor
9. Novel Approach to Treat Alzheimers and Other Diseases Offered by Targeting Cell Membrane RAFTS
10. CuraGen Sells Ownership of Belinostat to TopoTarget A/S
11. TopoTarget Successfully Buys Back Full Control of Belinostat
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Avalanche photodiodes target bioterrorism agents
(Date:6/23/2016)... Seattle, WA (PRWEB) , ... June 23, 2016 ... ... technology, announces the release of its second eBook, “Clinical Trials Patient Recruitment and ... patient recruitment and retention in this eBook by providing practical tips, tools, and ...
(Date:6/23/2016)... 23, 2016   Boston Biomedical , an ... designed to target cancer stemness pathways, announced that ... Orphan Drug Designation from the U.S. Food and ... cancer, including gastroesophageal junction (GEJ) cancer. Napabucasin is ... inhibit cancer stemness pathways by targeting STAT3, and ...
(Date:6/23/2016)... June 23, 2016 A person commits a crime, ... scene to track the criminal down. An outbreak ... and Drug Administration (FDA) uses DNA evidence to track down ... Sound far-fetched? It,s not. The FDA has increasingly used ... investigations of foodborne illnesses. Put as simply as possible, whole ...
(Date:6/23/2016)... ... June 23, 2016 , ... ... (Yeast and Mold) microbial test has received AOAC Research Institute approval 061601. , ... tests introduced last year,” stated Bob Salter, Vice President of Regulatory and Industrial ...
Breaking Biology Technology:
(Date:5/20/2016)...  VoiceIt is excited to announce its new ... By working together, VoiceIt and VoicePass will offer ... take slightly different approaches to voice biometrics, collaboration ... usability. Both ... "This marketing and technology partnership allows ...
(Date:4/28/2016)... SAN FRANCISCO and BANGALORE, India ... part of EdgeVerve Systems, a product subsidiary of Infosys (NYSE: ... service provider, today announced a global partnership that ... convenient way to use mobile banking and payment services. ... Mobility is a key innovation area for financial services, but ...
(Date:4/15/2016)... 15, 2016  A new partnership announced today ... underwriting decisions in a fraction of the time ... and high-value life insurance policies to consumers without ... With Force Diagnostics, rapid testing (A1C, Cotinine and ... (blood pressure, weight, pulse, BMI, and activity data) ...
Breaking Biology News(10 mins):