Produces pure P2 species (P2/P4 > 150)
Fast, stable and reproducible flux control
Large crucible capacity of 420 cm3
Safe cell loading and operation
Reliable large cross section cone valve
No hot cracker zone
Injector length and flux distribution adjustable
to fit most MBE systems
The Valved GaP Compound Source VGCS is a high purity P2-source, based on the decomposition of high purity GaP. The concept is derived from our DECO effusion cells to which a mechanical valve mechanism is added for rapid beam flux control.
Full MBE compatibility is reached by the integrated Gallium-Trapping-System, the integrated water cooling as well as the use of high purity inert materials such as pyrolytic boron nitride for all parts in the direct phosphorus path.
In contrast to sources using elemental phosphorus only minor amounts of white phosphorus are formed within the cell and the formation of white phosphorus within the MBE chamber is significantly reduced due to the direct formation of P2 species from the decomposition of single crystal GaP chunks with purity 6N-7N.
Operation of the mechanical valve unit shows fast, stable and reproducible flux control. Together with our valve controller easy handling and integration to your MBE system is provided.
The design of the valve mechanism is schematically illustrated on the right side. It provides a large cross section opening which allows very good pumping of the GaP reservoir. The robust wide angle valve design effectively elimitates the chance of locking, which is a frequently observed problem for needle valves.
Schematic illustration of the VGCS valve design
The figure on the right hand side shows the beam equivalent pressure (BEP) at the substrate position measured as a function of the valve position.
|High purity of GaInP layers grown on GaAs is demonstrated by SIMS measurements (see figure on the left).
The contamination of the GaInP layer with oxygen and carbon is below the detection limit of about 5x1016 cm-3 using highest purity single crystal GaP source material. The high performance of the phosphorus source allows growth of high quality GaInP/AlGaInP laser diodes or other P-compounds.
|BEP vs. time, with the valve on and off.
The P2 pressure can be switched by about two orders of magnitude.
|BEP during ramp up of the reservoir temperature from 800 to 1000°C.
The flux can be adjusted within minutes, due to the high reservoir temperature.
Valved Elemental Phosphorus Cracker
Valved GaP Compound Source (VGCS)
handling + safety
The VGCS is designed for growth of phosphide compounds in III-V-MBE. It has been readily approved in industrial applications. The fast and reproducible flux control using a valve allows the growth of phosphide-arsenide heterostructures with very sharp interfaces like quantum wells and superlattices. It is perfectly suited for applications in HEMTs, HBTs, GaAlInP laser diodes and other devices. Also GaInP/InP quantum dot lasers have been prepared. Moreover, very good results for pseudomorphic high electron mobility transistors have been achieved.
Very sharp transitions of P are achieved by application of VGCS and VACS sources at one deposition run. 300nm GaInP are deposited on a GaAs buffer layer on a (100) GaAs substrate. Due to the fast flux control properties of the valve unit P is sharply reduced on the GaInP/GaAs interface as demonstrated by the SIMS measurement on the right.
There are several publications for GaP decomposition source and valved GaP compound source. Please have a look at section References / List of Publications.
|2 separate heater-circuits (cell / valve)
|W5%Re/W26%Re (type C); 2 thermocouples (cell/valve)
|cell crucible: 800-950°C; valve: 350°C
|cell crucible: 1300°C; valve: 500°C
|integrated water cooling shrouds
|integrated valve unit
|servo motor drive with control unit MVCU
|Schematic drawing of the Valved GaP compound Source VGCS
VGCS 100-420 with VADAP adapter)
For general information on CF mounting flanges see Flange and Gasket dimensions.
|[mm] / [mm]
|[W] / [A]
|cell: 600 / 12
injector: 150 / 7
|cell: PS 70-22-C
injector: PS 30-10-C
|other mounting flange diameters feasible in combination with VADP adapter flanges (on request)
|other capacities on request
|specify UHV length L with order
e.g. VGCS 100-420-L300D57
is a valved GaP compound souce on DN100 CF flange with 420cm³ crucible and UHV-length 300mm.
The following list provides suggestions for related products. For additional product suggestions or more detailed information, please contact us.
|GaP Decomposition Source
|Motorized Valve Control Unit
|Beam Flux Monitor