Quantifying electric fields in semiconductor devices: The schematic shows electric field distribution in the channel of a GaN transistor; laser beams highlight the second harmonic generation (SHG) nature of the technique Image: Yuke Cao.

Energy loss is a major issue for efficient power electronics in applications such as solar or wind turbine stations, which feed into the national grid, electric cars, trains and planes.

Electric fields drive the degradation of wide-bandgap semiconductor devices, and directly mapping them inside an active device region has remained difficult.

But a reduced energy loss — if that were possible — means societies do not need to produce as much energy in the first place.

Cue the scientists at the University of Bristol’s School of Physics, who recently proposed a new way to quantify this electric field precisely.

They have done this by establishing how to remotely measure the electric field inside a semiconductor device for the first time, the school announced in a press release.

A semiconductor is a material, such as Silicon, which can be used in electronic devices to control electric current.

According to a study in Nature Electronics, scientists can now precisely quantify this electric field, meaning next generation power and radio frequency electronic devices can be developed which have the potential to be faster, more reliable and energy efficient.

Semiconductor device design can be trial and error, though more commonly it is based on a device simulation which then provides the basis for the manufacture of the semiconductor devices for real life applications.

When these are new and emerging semiconductor materials, it has often been unknown how accurate and correct these simulations actually are.

“Semiconductors can be made to conduct positive or negative charges and can therefore be designed to modulate and manipulate current,” said Prof. Martin Kuball at the University of Bristol.

“However, these semiconductor devices do not stop with Silicon, there are many others including Gallium Nitride (used in blue LEDs for example).

“These semiconductor devices, which for instance convert an AC current from a power line into a DC current, result in a loss of energy as waste heat — look at your laptop for example, the power brick is getting warm or even hot. If we could improve efficiency and reduce this waste heat, we will save energy,” he said.

“One applies a voltage to an electronic device, and as a result there is an output current used in the application. Inside this electronic device is an electric field which determines how this device works and how long it will be operational and how good its operation is.

“No one could actually measure this electric field, so fundamental to the device operation. One always relied on simulation which is hard to trust unless you can actually test its accuracy.”

To make good performance and long lasting electronic devices out of these new materials it is important that researchers find the optimal design, where electric fields do not exceed the critical value which would result in their degradation or failure.

Experts plan to use newly emerging materials such as Gallium Nitride and Gallium Oxide rather than Silicon, allowing operation at higher frequency and at higher voltages, respectively, so that new circuits are possible which reduce energy loss.

This work by the University of Bristol group will provide an optical tool to enable the direct measurement of electric field within these new devices.

“Considering that these devices are operated at higher voltages, this also means electric fields in the devices are higher and this in turn means they can fail easier,” said Prof Kuball.

“The new technique we have developed enables us to quantify electric fields within the devices, allowing accurate calibration of the device simulations that in turn design the electronic devices so the electric fields do not exceed critical limits and fail.”

Within an academic context, Prof. Kuball and his team will engage with partners within the US Department of Energy ULTRA centre, they are partnered in, to use this technique to make ultra-wide bandgap device technology a reality, allowing potential energy savings in excess of 10% across the globe.

“This development helps the UK and the world to develop energy saving semiconductor devices, which is a step towards a carbon neutral society,” he added.

Sources: University of Bristol, Tech Explorist