PSI - Group
Diamond Electronics
Introduction
Diamond may in many senses be regarded as an industrialist's dream material. Every physical, chemical and optical property represents an extreme as compared to other materials. In principle, one could fabricate the best tools, coatings, windows, microchips and so on, if only it were possible to engineer the material to suit the applications. It is the development of these high tech diamond modification, processing and packaging techniques through an understanding of the physics and electronics of diamond, which is the basis of this research. An additional program is to commercialize the technology.

Diamond research is now reaching payback time. Nontrivial volumes and surface areas of diamond can be synthesized hundreds of time more perfectly than nature can produce it at its best. The very recent advent of electronic device quality diamond is especially exciting. The so-called "low hanging fruit" will now be plucked. These are devices that require pure diamond (for radiation detectors) or diamond doped to p-type semi-conductivity with phosphorous. This is a relatively deep dopant, but a class of diodes can be fabricated, which are excellent for high voltage-high power and high temperature applications. When used as a detector in spacecraft these detectors are exposed to high temperatures of up to 500 C.  Due to its large band gap, this can easily be achieved by diamond devices.  In this case the “deep” nature of the P-dopant does not matter any more! The applications will at first be exotic and specialized, as the costs of diamond devices are currently high. However, it is envisaged that research will make these applications competitive. The commercialization drive will then support a range of scholarly investigations into the material.

The figure below identifies diamond as the only wide band gap high combined carrier mobility semiconductor (thermal conductivity proportional to the size of the circle)

Electronic diamond
The incentive to produce diamond electronics relates to the following favourable properties.
 

Combined Carrier Mobility

me x mh

>16 x 1016 cm2.V-1.s-1

High frequency capability, fast response times

Resistivity

s

>1 x 1011 W.cm-1

Low noise, low switching voltage, small feature size, ideal CMOS device

Breakdown Field

Eb

1 x 107 V.cm-1

High voltage capacity

Thermal Conductivity

st

25 W.cm-1.K-1

High power capacity, high integrability

Specific Ionisation Loss

dE/dx

46.9 eV/mm

Charge carrier generation as a detector. (Average number).

Vacancy tolerance

 

1020 cm-3

Radiation Hard

Dopant Immobility

 

 

The (weakness) difficulty in fabricating diamond electronics corresponds to the (strength) survival of devices in harsh environments

Taken together, as just one example this gives a diamond diode a Figure of Merit (FoM), which is thousands of times better than silicon.

Material BFM Figure of Merit
for high Power devices
Carrier Lifetime (ns)
 
Si 1  
4H-Si-C 290  
GaN 910  
Best Synthetic   8
Best Natural 8600 1-10
New SC CVD Diamond >17000 2000





Our program has the following components

  1. Develop shallow molecular dopant systems using heavy-ion implantation into 
    diamond with a specific defect - anneal history, and then follow a solid state
    chemistry strategy
  2. Develop diamond detectors in collaboration with E Berdermann of GSI
  3. Correlation between electronic properties, defects, synthesis in collaboration
    with A Freund, J Horzowska and J Haertig of the ESRF
  4. Hydrogen behavior in diamond
  5. Muonium as a hydrogen analogue in diamond