A new method to detect infrared energy using a nanoporous ZnO/n-Si photodetector

July 1, 2014
This is the photoresponse of the nanoporous ZnO/ n-Si sample under the illumination of a 1064 nm laser pulse at varying energy levels. The symbols t1 and t2 represent the corresponding time of the transient voltage peaks. The inset shows the linear relationship between the time interval, i.e. (t2-t1), and the laser pulsed energy. Credit: Science China Press

Experiments aimed at devising new types of photodetectors have been triggered by the increasing use of optoelectronic devices in personal electronics, cameras, medical equipment, computers and by the military. Professor Zhao Kun and co-researchers at the State Key Laboratory of Petroleum Resource and Prospecting, part of the China University of Petroleum in Beijing, have proposed a new type of infrared photodetector.

Photodetectors, which can convert photons to electrical signals, are used to observe and measure the wavelength or energy of light, including , which is beyond the visible spectrum. Many different types of photodetectors have been widely used in , such as digital cameras or . Scientists around the world are constantly exploring the potential to devise, or are actually developing, new generations of photodetectors that feature new configurations or new materials.

Zhao and colleagues state in a new study, "Double peaked decay of transient photovoltage in a nanoporous ZnO/n-Si photodetector," that this ZnO/n-Si structure has an application as a new, simple and low-cost photo-energy detector for an infrared pulsed laser. The paper was published in SCIENCE CHINA Physics, Mechanics & Astronomy.

Zinc oxide (ZnO) is a low-cost and environment-friendly semiconductor. It has a wide band gap (~3.37 eV) at room temperature, so that only ultraviolet light (with a wavelength less than 400 nm) can be absorbed effectively. In terms of photodetector applications, ZnO and ZnO-based devices are routinely studied as an photosensor.

Yet researcher Zhao and his group now report that when ZnO is combined with n-type Si, an interesting photoresponse is observed under near infrared pulsed light irradiation. "In the present work, we propose a type of infrared photodetector based on a nanoporous ZnO/n-Si structure, which is synthesized by a simple sol-gel method," they state in the study. "Under illumination of one infrared laser pulse, this porous structure exhibits a double peak on a millisecond time scale in the decay of transient photovoltage."

As the structure was irradiated by a pulsed laser with a wavelength of 1064 nm, one laser pulse with energy of 0.072 mJ triggered two peaks: a higher photovoltaic (HPV) peak with an amplitude of ~235 mV and a succeeding lower photovoltaic (LPV) peak with an amplitude of ~13 mV. The (t2-t1) was ~99.64 ms; t1 and t2 represent the corresponding time of the related transient photovoltaic peaks (as shown in Figure 1).

When the pulsed energy increased from 0.072 mJ to 0.332 mJ, the amplitude of the corresponding higher photovoltaic peaks increased from ~235 mV to ~275 mV. In contrast, the amplitude of the LPV peaks remained almost the same, that is, ~13 mV. The authors posited that this particular photoresponse of the nanoporous ZnO/n-Si structure originated from the synergy of the photoelectric effect and the photo-thermal excitation process.

Most importantly, the time interval between the double peaks of transient photovoltage is highly sensitive to slight changes in the energy of the laser pulse. When the irradiated pulsed energy is increased, the time interval (t2-t1) increases linearly.

This characteristic indicates that the nanoporous ZnO/n-Si structure has the potential to be developed into a new, inexpensive for an infrared pulsed laser.

Explore further: High efficiency infrared photodetectors using gold nanorods

More information: Liu H, Fu C, Zhao K., "Double-peaked decay of transient photovoltage in a nanoporous ZnO/n-Si photodetector" Sci China-Phys Mech Astron, 2014, 57 (6): 1201-1205. DOI: 10.1007/s11433-014-5459-4

Related Stories

High efficiency infrared photodetectors using gold nanorods

March 25, 2011

Toyohashi Tech researchers develop an innovative infrared photodetector exploiting ‘plasmon resonance’ at the surface of gold nanorods. This technology shows potential as the basis for the development of high efficiency ...

Exposing ZnO nanorods to visible light removes microbes

May 12, 2011

The practical use of visible light and zinc oxide nanorods for destroying bacterial water contamination has been successfully demonstrated by researchers at the Asian Institute of Technology (AIT). Nanorods grown on glass ...

Self-powered wireless light detectors

March 12, 2014

Light detectors are used extensively in daily life as brightness sensors and as receivers for remote control devices in electrical gadgets, for example. However, operating these detectors requires electrical energy, which ...

Chemical sensor on a chip

June 11, 2014

Using miniaturized laser technology, a tiny sensor has been built at the Vienna University of Technology which can test the chemical composition of liquids.

Recommended for you

Magnetism at nanoscale

August 3, 2015

As the demand grows for ever smaller, smarter electronics, so does the demand for understanding materials' behavior at ever smaller scales. Physicists at the U.S. Department of Energy's Ames Laboratory are building a unique ...

Study calculates the speed of ice formation

August 3, 2015

Researchers at Princeton University have for the first time directly calculated the rate at which water crystallizes into ice in a realistic computer model of water molecules. The simulations, which were carried out on supercomputers, ...

Small tilt in magnets makes them viable memory chips

August 3, 2015

University of California, Berkeley, researchers have discovered a new way to switch the polarization of nanomagnets, paving the way for high-density storage to move from hard disks onto integrated circuits.

Scientists bring order, and color, to microparticles

August 3, 2015

A team of New York University scientists has developed a technique that prompts microparticles to form ordered structures in a variety of materials. The advance, which appears in the Journal of the American Chemical Society ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

plaasjaapie
not rated yet Jul 01, 2014
Pretty slow response time. :-(

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.