The Next Leap in Semiconductors
Increasing the capabilities of modern chips is often simplistically boiled down to how many transistors can fit onto a piece of semiconductor. This is why the biggest names in semiconductor production, including Intel and AMD, are constantly trying to shrink the size of transistors down. However, this shrinking can only go on for so long before it becomes either impossible to make transistors smaller or no longer financially viable to do so.
This problem has created a very real need to find the next semiconducting material that could open the door for continued advancements (and, consequently, for faster and better devices).
Silicon has served the tech industry well, but its days as the go-to semiconductor material may be numbered.
Silicon, the wonder material. Image courtesy of Massimiliano Lincetto (own work) [CC BY-SA 4.0]
The quest for silicon's replacement as a semiconductor has been ongoing for years now. Recently, researchers have investigated tapping carbon nanotubes as a replacement for silicon or using insulating MOFs as an alternative semiconductor. Other teams are focusing their efforts on bypassing semiconducting material altogether with metamaterials that function like tiny valves.
However, Professor Mutsuko Hatano and Tokyo Tech believe that diamond could be the looking glass in which the next semiconductor material lies.
The Properties that Make Diamond Shine
Diamond is a truly amazing material. It's incredibly strong (due to its 3D structure and covalent bonds), near-transparent, and has high thermal conductivity. However, diamonds are also very good electrical insulators which strangely is both useful and problematic for electrical devices.
Table showing diamond properties against other materials. Image courtesy of Tokyo Tech
The insulative ability allows for larger voltages and smaller leakage currents while the lack of conductivity means that electricity will not flow. However, the electrical conductivity can, in fact, be changed in an almost identical fashion to semiconductor doping.
Using elements such as phosphorus and boron, diamond can be doped with n-type and p-type materials which increase the electrical conductivity of diamond.
So if diamond can be doped and potentially make better semiconductor devices than silicon, why has it not been done yet? The answer lies in the ability to make a p-n junction in diamond.
Simplification of a p-n junction. Image used courtesy of Raffamaiden (own work) [CC BY-SA 3.0]
Making an n-type or p-type doped diamond is not a challenge, itself, but making a piece of diamond that contains both close enough to create a p-n junction is very challenging.
However, Professor Mutusko Hatano, along with the National Institute of Advanced Industrial Science and Technology, has made a lateral p-n junction on diamond which was then created into a J-FET prototype.
Diamond devices would have significant impacts on high-power devices primarily due to diamond's electrical resistivity and heat dissipation capabilities. The very high electrical resistivity would allow for very high-voltage-rated devices which would be beneficial in applications including power distribution and high voltage handling (such as electric trains). The heat conductivity would allow for smaller power devices as the diamond material could help to dissipate more heat (which would keep the device cooler for larger current draw as compared to current silicon devices).
Diamond Sensors on the Horizon
Professor Hatano has bigger plans for the diamond semiconductor. Her plan is to create diamond sensors which could be used for analysis of protein structures, cell measurements, and drug delivery systems.
Diamond test sensor using nitrogen doping to detect magnetic fields. Image courtesy of Tokyo Tech
Diamonds clearly show real promise in the semiconductor field, earning a serious place in the running to become the next power semiconductor material. At present, diamonds cannot be manipulated and grown in the same fashion as current semiconductor devices (where a very large single crystal of silicon can be drawn out of a molten crucible). But if someone can crack the case of diamonds, material science and engineering as a whole could be in for a new age.