New Phototransistor to Speed Up Digital Cameras

Engineers have crafted a new silicon phototransistor which they claim is the fastest so far and would drastically improve the performance of products which rely on electronic light sensors such as digital cameras, night-vision goggles and smoke detectors.

Integrated into a digital camera lens, for example, it could reduce bulkiness and boost both the acquisition speed and quality of photos and videos, the University of Wisconsin-Madison engineers said.

Like human eyes, phototransistors sense and collect light, then convert that light into an electrical charge proportional to its intensity and wavelength.

In the case of our eyes, the electrical impulses transmit the image to the brain. In a digital camera, that electrical charge becomes the long string of 1s and 0s that create the digital image.

While many phototransistors are fabricated on rigid surfaces, and therefore are flat, the new product is flexible, meaning it more easily mimics the behaviour of mammalian eyes.

"We actually can make the curve any shape we like to fit the optical system," said professor Zhenqiang Ma.

The researchers also placed electrodes under the phototransistor's ultrathin silicon nanomembrane layer - and the metal layer and electrodes each act as reflectors and improve light absorption without the need for an external amplifier.

"There is a built-in capability to sense weak light," Ma explained.

"It shows the capabilities of high-sensitivity photo detection and stable performance under bending conditions, which have never been achieved at the same time," the professor added.

The details of the study were published in the journal Advanced Optical Materials.