Silicon Could Be Key to Making Diamond Semiconductors a Reality

June 06, 2016 by Zabrel Holsman

Researchers from the University of Texas at Arlington and the University of Wisconsin-Madison have made a collective discovery in a new method for doping diamonds

Researchers from the University of Texas at Arlington and the University of Wisconsin-Madison have made a collective discovery in a new method for doping diamonds

Following the advent of new renewable energy resources and the increased demand to convert and deliver such energy efficiently, there has been a remarkable increase in power electronics market research. Scientists and researchers are aiming to make our current technology smaller and faster.

However, they have run into several issues with material limitations directly related to power performance and efficiency. There has been a gradual shift from the augmentation of materials to replacing them as they become physically optimized. 


The Reign of Silicon Semiconductors

Silicon has been the favored semiconductor material for over half a century now and still comprises nearly 95% of the market. Unfortunately, the advancement of silicon-based technology is limited by the physical nature of silicon. The materials and devices currently on the market are nearly perfect in terms of size and speed, leaving little room for improvement. The more apparent problem that silicon-based electronics have is heat management.


Silicon crystalline structure doped with boron. Image courtesy of Rice University.


What the industry has been looking for is a material that can be used as an alternative to silicon, but is faster, smaller, less hot, and much more powerful. Fortunately, there happens to be a material that can perform better in all these critical aspects of a semiconductor material: diamond.


Diamond Semiconductors Research

In the past decade, diamond has seen an increase in appeal due to its superior electrical properties and has been considered to be the finest candidate for use in the power electronics industry.

In comparison to its silicon counterpart, diamond can potentially exceed the relative efficiency of any silicon material property in regards to power electronics. Diamond can function as a wide-bandgap semiconductor, has a high critical field temperature for superconducting, has a superior carrier mobility, and, above all, it has the greatest potential for heat conduction out of any accessible material.


Image courtesy of Evince Technology.


The problem that scientists have had with using diamond is the fact that doping the crystals of diamond with boron calls for techniques that heat the diamond up to 1450 degrees Celsius. The issue with this was that the excess boron needed to be removed after the doping took place. Additionally, that technique only works effectively with diamonds that contain numerous crystals locked together into a single crystal. Diamonds that are composed of polycrystalline structures tend to have inconsistencies in the crystal structure that make them more difficult to work with.


Doping Single Crystalline Diamonds

recent research paper was published in the Journal of Applied Physics describes a new method for doping diamond crystals, greatly increasing their potential as a semiconductor.

As described in their paper, a team comprised of University of Texas at Arlington and University of Wisconsin-Madison researchers has made a collective discovery in a new method for doping diamonds. The teams demonstrated a simple and efficient method for the selective doping of single crystalline diamonds (SCD) using thermal diffusion at significantly lower heat than that of current techniques.

The secret ingredient to the method turns out to be silicon of all things. The team discovered that if they bonded the SCD with silicon that had already been doped with boron and heated to eight hundred degrees Celsius, the boron would shift from the silicon to the diamond. This occurs due to the diamonds' naturally shifting carbon, which leaves gaps for the boron atoms to fill.


A single crystalline diamond plate. Inset: Anode metal on doped silicon. Image credit: Jung-Hun Seo. Image courtesy of AIP Publishing.


The method described in their paper only addresses p-type semiconductors; a new method for doping n-type semiconductors is still a ways away.

The team intends to focus on manufacturing a device made of the p-type SCDs. However, if researchers intend to create components like a transistor, then n-type semiconductor doping needs to be realized as well.