editor's blog
Subscribe Now

Piezo… what?

The piezoelectric effect is pretty straightforward. With certain crystals, if you apply strain, the separation of dipoles in the crystal will set up a piezopotential.

Let’s take that one step further by making contacts on either end of a nanowire made of an appropriate material – in particular, ZnO, but potentially other so-called “wurtzite” semiconductors. Put a potential across is and use mechanical stress in the nanowire to modulate the current: you’ve basically got a FET, with the nanowire acting as a mechanical gate.

Those contacts are Schottky contacts, and the strain allows the Schottky barrier to be raised. But if you shine an appropriate laser on the contact, you can create electron-hole pairs, lowering the Schottky barrier, and even making the contact Ohmic instead.

This three-way interplay between the piezopotential created by strain, the optical excitation, and the transport properties of the semiconductor is referred to as piezophototronics. Say it slowly until you get used to it so you don’t hurt yourself.

How is that useful? Well, for one thing, it can be used, as was just demonstrated at Georgia Tech, to increase the performance of a GaN LED by forming a junction between a GaN film and a ZnO nanowire. The interface formed a p-n junction, with the GaN being the p side and the nanowire being the n side.

By straining the nanowire, they could tune the charge transport and effectively increase the rate of electron-hole recombination, increasing the overall efficiency by 4 times.

That’s the condensed version, the bottom line. You can get more details in their recent release.

Leave a Reply

featured blogs
Apr 22, 2019
Last week, Cadence announced the certification of its LPDDR4 IP in TSMC's 16nm automotive process. The opening paragraph of the press release actually says: Cadence Design Systems, Inc today... [[ Click on the title to access the full blog on the Cadence Community site....
Apr 19, 2019
As platforms become more electrical, and the safety of flying becomes paramount, the FAA'€™s EWIS regulations serve as a cornerstone to modern aircraft wiring compliance and safety certification. EWIS (rhymes with '€œGee whiz'€) is both a concept and practice that embr...
Apr 18, 2019
Thermal Shock testing isn’t unique to the connector world, but it does play a big role in the qualification testing that Samtec puts all connectors through before they are released for production. Chances are likely that you thermally shock many items per day and don...
Jan 25, 2019
Let'€™s face it: We'€™re addicted to SRAM. It'€™s big, it'€™s power-hungry, but it'€™s fast. And no matter how much we complain about it, we still use it. Because we don'€™t have anything better in the mainstream yet. We'€™ve looked at attempts to improve conven...