Tech Insights

Can Diamond Diodes Power High-Voltage Devices?

December 10, 2023 by Jake Hertz

An Illinois research team claims it has developed a diamond-based electronic device well-suited for high-power electronics.

A key trend in semiconductor material is the use of diamond, which offers superior properties compared to traditional silicon semiconductors. Diamond has exceptional thermal conductivity, high carrier mobility, and large bandgap, making it a promising material in semiconductors for power electronics.

 

Diamonds.

Diamonds. Image used courtesy of Unsplash

 

Recently, researchers from the University of Illinois Urbana-Champaign achieved a breakthrough in diamond-based semiconductors that could redefine the landscape of high-power electronic devices. 

 

A Background on Diamond Semiconductors 

Diamond semiconductors stand out due to the intrinsic properties of diamond materials.

With a bandgap of 5.47 eV, diamond has a much larger bandgap than silicon (1.12 eV) or even silicon carbide (3.26 eV). This large bandgap enables high breakdown voltages and low leakage currents, making diamond an excellent candidate for high-power and high-frequency applications. Additionally, diamond’s high thermal conductivity (22 - 24 W/cm·K) is beneficial for dissipating heat in high-power devices, a critical factor in ensuring reliability and longevity.

 

The diamond semiconductor device.

The diamond semiconductor device. Image used courtesy of the University of Illinois Grainger College of Engineering

 

The challenge in harnessing these properties lies in the fabrication of diamond-based devices. One such technique is chemical vapor deposition, refined to grow high-quality diamond films. P-type doping of diamond, often with boron, has been achieved with relatively low activation energy, enhancing the feasibility of creating diamond-based electronic devices. However, the difficulty in attaining n-type doping and the complexity of processing diamond materials have been significant hurdles.

A particular focus has been developing diamond-based Schottky barrier diodes (SBDs), crucial for power rectification and switching applications. These devices have shown promise in achieving high breakdown voltages and low on-state resistances, but there is a continuous effort to push these parameters further, enhancing the efficiency and power handling capabilities of diamond SBDs.

 

Advances in Diamond Schottky Barrier Diodes

A recent study of SBDs has made a notable advancement in diamond semiconductor technology. Specifically, the researchers have successfully fabricated diamond p-type lateral Schottky barrier diodes with an impressively high breakdown voltage of 4612 V at a current density of 0.01 mA/mm. 

 

Forward J-V characteristics of the diamond lateral SBD with and without the field plate.

Forward J-V characteristics of the diamond lateral SBD with and without the field plate. Image used courtesy of Han et al.

 

The key to this advancement lies in using aluminum oxide (Al2O3) field plates in the device structure. The Al2O3 field plates reduce the peak electric field, enhancing the breakdown voltage. This design circumvents the need for a thicker drift layer, a typical approach to increasing breakdown voltage, which is challenging to achieve in diamond due to growth and etching difficulties.

The diodes exhibit rectifying ratios larger than 10^7 at room temperature and a peak current density of 5.39 mA/mm under a 40 V forward bias at 200°C. Furthermore, the leakage current density at room temperature remains stable at approximately 0.01 mA/mm for both diodes, with and without Al2O3 field plates. The use of Al2O3 not only improves the breakdown voltage but also maintains stable leakage current characteristics, a crucial factor for reliable device performance.

 

A Power Breakthrough?

The researchers’ breakthrough in achieving a high breakdown voltage in diamond p-type lateral SBDs marks a significant step in using diamond as a semiconductor material for power electronics. Most notably, their findings signify a move closer to overcoming the challenges associated with diamond semiconductor fabrication, paving the way for more efficient and robust power electronic devices. As the technology matures, we can expect diamond-based devices to play a pivotal role in sectors ranging from renewable energy to electric vehicles, offering a more sustainable and efficient electronic future.