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  • MBE growth; GaP, GaInP, etc.
  • P doping in Si MBE
  • Arsenides
  • Dimer:tetramer ~1000:1
  • P2/As2:Ga >104:1
  • Standard K-Cell controllers
Compound Dissociation K-Cell
Phosphorus, Arsenic - Low cost alternative to valved crackers
Although it has been known for many years that the thermal decomposition of GaP/InP and GaAs/InAs produce substantially P2 and As2 respectively(1), only recently has this method been seriously applied in MBE as a simpler, lower-cost alternative to two-zone valved crackers(2) which operate with elemental red phosphorus (P4) feedstock. On heating, red phosphorus sublimes and converts to the white P4 allotrope, which must then be thermally cracked from a secondary buffer zone to produce the reactive P2 species. In contrast, the CDK35 is a compound dissociation source consisting solely of a K-cell and a Ga trap. The source produces a beam of dimeric phosphorus/arsenic with extremely low parasitic Ga content and tetramer species.

The K-cell is simple to use and maintain and provides stable, reproducible deposition rates. It can be used for applications requiring high growth rates, such as phosphides; or for doping applications.

For GaP decomposition the dominance of P2 over P4 is ~ 1000:1 at a dissociation temperature of 950ÂșC. However, there is also a significant (and undesirable) contribution of Ga vapour at this temperature.

Figure 1 shows the partial pressures of Ga and P2 using the source without the Ga trap. The P2/Ga ratio is only 6:1. Figure 2 shows the partial pressures of these species with the Ga trap fitted. By this means a P2/Ga ratio of ~104:1 can be achieved (3).


Model CDK35

In-vacuum diameter 34mm

In-vacuum length 200mm (standard)

Mounting flange NW35CF

Operating K-cell temperature to 1000oC<

Crucible PBN - 35 cm3*

Power supply Included

Water cooling Included

Options Shutter (NW63CF flange required)

* Higher capacity available on request
(1) Farrow, R.F.C., J. Phys D. 7 pp2436 (1974)
(2) Song, J.D, et al., J.Cryst. Growth 237-239 pp1504 (2002)
(3) Oxford Applied Research mass spectra (unpublished)

Download brochure in PDF format: CDK35