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DECO-D 40-10-22-KS Phosphorus doping source, on a flange DN40 CF (O.D. 2.75"), with 10 cm³ PBN crucible and Ga-trapping PBN cap

• 10²⁰/cm³ n-type doping in Si/SiGe MBE
• P-doping through GaP decomposition
  
• High P incorporation rate
• Minimum memory effects
• Easy to install and to operate
• Sharp doping profiles
• Precise and fast flux control

The Phosphorus Doping DECO-D is an ultra pure source for P₂, based on the decomposition of GaP. At typical operation temperatures of about 600°C - 700°C GaP is essentially decomposed to Ga and P₂. Additional cracking is not necessary and the accumulation of P₄ (White Phosphorus) is reduced to a minimum.

The simple construction of the DECO-D, 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-D is comparable to usual effusion cells and does not require complicated mechanical valves and controllers. MBE-Komponenten GmbH has developed special sources based on the Ga-Trapping-Cap System. We build the DECO-D optimized for special doping applications, e.g. as phosphorus doping cell for Si MBE with a reduced cell shutdown time.

The heater of the DECO-D 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.

Principle of operation of the Ga-Trapping-Cap-System

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.
In addition to the complete DECO we offer the Ga-Trapping-Unit as a product of its 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 temperatures 900-1200°C for growth applications
• very good temperature and flux control
• fast switch of flux
• very stable and reproducible flux
• precise P₂ control in GaAsP, GaInAsP etc. compounds
• P₂/P₄ ratio about 150
• very low parasitic Ga flux (P : Ga > 10³)
• high efficiency: about 10 g P in GaP for
  100 µm film thickness
• scarcely any white P accumulation in MBE system
• no additional safety facilities needed in contrast to PH₃, AsH₃ or valved elemental Phosporus crackers
• no bakeout necessary before opening the system
• compatible with standart III/V solidsource MBE
• requires no additional pump
• simple but effective design

Application

Typical applications of our DECO-D phosporus doping source are high level and sharp delta-doping with Phosphorus in Si/SiGe MBE. Small crucible charges, large double layer shutters, integrated water cooling and reduced shielding allow a fast shutdown of the cell after the doping. High 10²⁰/cm³ doping and sharp delta-doping have been reported in literature applying the DECO-D from MBE-Komponenten GmbH. Due to its small dimensions and easy operation the DECO-D is ideally suited for all types of MBE systems.
Single crystal GaP material with a purity >6N is recommended as source material.

The DECO-D has been successfully operated in many MBE laboratories worldwide. The following three figures demonstrate the unique performance of devices fabricated by means of the DECO-D.

The figure below shows a sharp P-doping profile in a Si layer with two P-delta-layers. The experiment was performed at the Universät der Bundeswehr in Munich, in the group of Prof. Eisele.

SIMS measurement of phosphorus delta-doping in Si-MBE with a DECO-D 40-10-22-KS;
(Data courtesy of C.Tolksdorf, Physics Institute ET9, Uni-BW Munich)

The figure on the right shows an I-U characteristic with a record high peak-to-valley current ratio of a Si/SiGe Esaki diode. The data are from R. Duschl et al., Appl. Phys. Lett. 76 (2000) 879, measured at the Max-Planck-Institute for Solid State Research in Stuttgart.

I-U characteristic of a Si/SiGe Esaki diode

On the last figure a SIMS profile of a sharp p-n junction in a Si/SiGe/Si Esaki diode decice is presented. The structure was grown at the Max-Planck-Institute for Solid State Research in Stuttgart, in the group of Dr. O. Schmidt. It shows a record high peak-to-valley current ratio.

SIMS profile of a Si-based Esaki diode with a
sharp p-n junction.

Technical Data

Dimensions

Specific Data

For general information on CF mounting flanges see "Flange and Gasket Dimensions".

System manufacturer:    MBE-Komponenten, Omicron and other manufactures not separately listed
				[cm³]	[mm]			Type	[mm] / [mm]		[W] / [A]	Product Code	Product Code
		DECO-D	40 -	10 -	22 -		S* -	C -	LxxxD34		120 / 6	PS 30-10-C	PBN 10-22
		DECO-D	40 -	10 -	22 -	K	S* -	C -	LxxxD36		120 / 6	PS 30-10-C	PBN 10-22
		DECO-D	40 -	35 -	34 -		S* -	C -	LxxxD35		180 / 7	PS 30-10-C	PBN 35-34
		DECO-D	63 -	35 -	34 -	K	S* -	C -	LxxxD60		240 / 8	PS 30-10-C	PBN 35-34

 LAST UPDATE: MARCH, 2006

© 2003 Dr. Eberl MBE-Komponenten GmbH