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DECO 40-60 GaP decomposition source for Phosphorus (P2) , on a flange DN40 CF (O.D. 2.75"), with 60 cm³ PBN crucible and Ga-trapping PBN cap

• Ultra high purity Phosphorus (P₂) source
• Compatible with most MBE systems
  
• Effusion cell-like operation
• Safe and pure doping or growth techniques
• Various crucibles, capacity 10-200 cm³
• Simple construction, low cost, high reliability
• Precise and fast flux control
• Optional: on cell flange integrated cooling shroud and shutter

The Decomposition Source - DECO - is an ultra pure source for P₂ based on the decomposition of GaP.

The simple construction of the DECO, based on our WEZ and PEZ cells, and the specially designed Ga-Trapping-Cap System have the advantages of easy mounting, full compatibility to all MBE systems, high reliability and low cost. The operation of the DECO is comparable to usual effusion cells and does not require complicated mechanical valves and controllers. Compared to the operation of an often used valved cracker the deposition of white phosphorus (P₄) within the growth chamber is significantly reduced due to the direct generation of pure P₂.

MBE-Komponenten GmbH has developed special sources based on the Ga-Trapping-Cap System. We build the DECO optimised for growth applications with high evaporation rates and large crucible capacities or alternatively optimised for special doping applications, e.g. as phosphorus doping cell for Si MBE with a reduced cell shutdown time.

The heater of the DECO is designed very similarly to the WEZ-heater which consists of a Ta wire filament supported by PBN rings. Crucible material is PBN.With this design minimum outgassing at operation temperature is achieved, in combination with excellent reliability, long-term stability and extended lifetime.

Excellent operation temperature stability of ±0.1°K is achieved by an improved design of the thermocouple assembly. This assembly touches the crucible near the base. The direct touch technique and the use of double pairs of TC-alloy wires ensure a reproducible and stable measurement of the real crucible temperature.

Ga-Trapping PBN cap on a DECO 63-125

PBN caps for DECO sources, different sizes

Ga-Trapping-Cap-System

MBE-Komponenten produces a unique system which provides a very pure P₂ beam by the decomposition of GaP. The Ga-Trapping-Unit, consisting of a few well designed parts, can be easily mounted on a standard effusion cell. The Ga-Trapping-Cap System is based on the sublimation of phosphorus from GaP. The parasitic Ga atoms are efficiently separated from the P₂ beam. Thus a very pure P₂ beam is produced.
The Ga-Trapping-Unit can be mounted on standard effusion cells without additional tools and materials, it also can be easily removed to change or refill the crucible.
Additional to the complete DECO we offer the Ga-Trapping-Unit as a product of it's own. Please contact us for further information.

Equilibrium pressures of the components along the metal-rich boundary of the field of solidus of a Ga-P system [R.F.C. Farrow, J.Phys. D, 7, 2436 (1974)]

• high operating temperature 1000°C
• very good temperature (flux) control
• fast switch of flux
• very stable and reproducible flux
• precise P₂ control in GaAsP GaInAsP etc. compounds
• P₂/P₄ ratio is about 150
• very low parasitic Ga flux (P : Ga < 10-3)
• high efficency: about 10 g P in GaP for 100 µm film thickness
• hardly any white P accumulation in MBE system
• no additional safety facilities needed in contrast to PH₃ or AsH₃ or valve elemental Phosporus crackers
• no backout necessary before opening the system
• compatible with standart III/V solidsource MBE
• no additional pump (ion pumps o.k.)
• simple but effective design

Application

Typical applications of our decomposition sources based on the Ga-Trapping-Cap System are the growth of phosphide compounds (GaInP, InP) in III-V MBE as well as Phosphorus doping (n-type) in Si MBE. MBE-Komponenten GmbH provides well designed standard effusion cells with the Ga-Trapping-Cap System. This GaP decomposition source DECO combines our most efficient heating system, known from our WEZ cells with the Ga-Trapping-Cap System. Thus a very stable and reproducible P₂ beam is achieved. Different DECO source designs are optimised for growth or for doping application. The Ga-Trapping-Unit and the DECO can be used as an As2 or Sb2 source, too. Valved DECO sources with larger capacities are available on request. Please ask for more information.

Technical Data

Dimensions

Specific Data

 LAST UPDATE: NOVEMBER, 2004

© 2003 Dr. Eberl MBE-Komponenten GmbH