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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 950ºC. 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). Specification 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 Growth 237-239 pp1504 (2002) (3) Oxford Applied Research mass spectra (unpublished) Download brochure in PDF format: CDK35
Last updated: 23rd July 2010 Copyright 2008 The Vacutec Group Home About Us News Conferences Contact Technical Support