News Article

Supressing Leakage In Nitride Diodes

Leakage currents in Schottky barrier diodes plummet by seven orders of magnitude when the barrier composition is shifted from Al0.21Ga0.79N to Al0.11Ga0.89N.

ENGINEERS from Central Research Lab, Hitachi, have shown that reverse leakage currents in AlGaN/GaN Schottky barrier diodes can plummet through reductions in sheet carrier density.

High leakage currents are an Achilles heel for today’s GaN diodes, which hold much commercial promise thanks to their combination of high temperature, high frequency and high power.

It is widely believed that the dominant cause of leakage is structural defects, especially dislocations, which can result from strain in the AlGaN layer.

However, initial studies by the Hitachi researchers indicated that sheet carrier density also influences leakage current.

This finding motivated these engineers to carry out further work involving three AlGaN/GaN heterostructures that shared a 3.6 μm, highly-resistive GaN buffer layer and a 5 nm GaN cap.

In these samples, barrier compositions were Al0.11Ga0.89N, Al0.16Ga0.84N and Al0.21Ga0.79N, and corresponding roomtemperature two-dimensional electron gas densities determined by Hall measurements were 3.6 x 1012 cm-2, 6.6 x 1012 cm-2 and 1.0 x 1013 cm-2, respectively.

“We prepared those three samples with our own MOCVD [tool] under precisely controlled conditions," says lead author Akihisa Terano. “We think that the material quality of our three samples is almost the same."


Figure 1. Schottky diodes built by Hitachi feature 1000 μm by 200 μm cathodes and anodes, separated by 200 μm

All three epiwafers were processed into planar Schottky barrier diodes with contacts formed by electron beam evaporation (see Figure 1).

Measurements on the devices revealed that a three-fold fall in the density of the two-dimensional electron gas results in a reduction in leakage current by seven orders of magnitude (see Figure 2).

Figure 2. Massive changes in leakage current result from relatively small changes in the density of the two dimensional electron gas

Unfortunately, slashing leakage current with this approach has its downsides.

“A reduction in the sheet density is thought to lead to some increase in the resistance of the drift layer, resulting in some decrease of the forward current," explains Terano.

He and his co-workers are now planning to tackle this issue head-on, developing devices that combine a sufficiently high forward current with a low leakage.

A. Terano et al. Electron. Lett. 48 274 (2012)

AngelTech Live III: Join us on 12 April 2021!

AngelTech Live III will be broadcast on 12 April 2021, 10am BST, rebroadcast on 14 April (10am CTT) and 16 April (10am PST) and will feature online versions of the market-leading physical events: CS International and PIC International PLUS a brand new Silicon Semiconductor International Track!

Thanks to the great diversity of the semiconductor industry, we are always chasing new markets and developing a range of exciting technologies.

2021 is no different. Over the last few months interest in deep-UV LEDs has rocketed, due to its capability to disinfect and sanitise areas and combat Covid-19. We shall consider a roadmap for this device, along with technologies for boosting its output.

We shall also look at microLEDs, a display with many wonderful attributes, identifying processes for handling the mass transfer of tiny emitters that hold the key to commercialisation of this technology.

We shall also discuss electrification of transportation, underpinned by wide bandgap power electronics and supported by blue lasers that are ideal for processing copper.

Additional areas we will cover include the development of GaN ICs, to improve the reach of power electronics; the great strides that have been made with gallium oxide; and a look at new materials, such as cubic GaN and AlScN.

Having attracted 1500 delegates over the last 2 online summits, the 3rd event promises to be even bigger and better – with 3 interactive sessions over 1 day and will once again prove to be a key event across the semiconductor and photonic integrated circuits calendar.

So make sure you sign up today and discover the latest cutting edge developments across the compound semiconductor and integrated photonics value chain.



Search the news archive

To close this popup you can press escape or click the close icon.
Register - Step 1

You may choose to subscribe to the Compound Semiconductor Magazine, the Compound Semiconductor Newsletter, or both. You may also request additional information if required, before submitting your application.

Please subscribe me to:


You chose the industry type of "Other"

Please enter the industry that you work in:
Please enter the industry that you work in:
Live Event