MBE Components, Thermal Gas Injector TGI

TGI

Thermal Gas Injector

TGI 40
  • Heated gas injection tube

  • No undesired gas cracking

  • No material condensation

  • Compatible with all MBE systems

  • Integrated water cooling shroud on request

  • Excellent reliability and long lifetime

  • Low power consumption

  • Option: high temperature cracking zone

TGI 40, thermal gas injector mounted on DN40 CF (O.D. 2.75") flange

 


The Thermal Gas Injector – TGI – is a heated injector tube  for the insertion of high vapor pressure materials or gases from an external gas reservoir or gas handling system into a vacuum chamber under high to ultra-high vacuum conditions (i.e. pressures less than 1x10-5   mbar). The TGI provides full compatibility with all UHV systems and standard III-V- molecular beam epitaxy.
The gas conductor tube is available from different materials  like Ta, Mo, PBN and quartz to allow the injection of corrosive  gases like O2 , AsBr3 , Cl2 , HCl etc. The tube is completely surrounded by a wire heater to avoid material condensation inside the tube (Fig. 1). The typical operation temperature range of the heater is between  100°C and 400°C which is too low for undesired gas cracking.

A high temperature cracking zone close to the nozzle is offered as an option. The high temperature cracker can be operated up to 1400°C. It allows defined thermal decomposition of the injected gas.

The nozzle on top of the injector tube comprises a specially designed shower head gas distributor produces an adequate angle gas beam for uniform gas distribution on the substrate.

The exclusive use of UHV compatible materials as well as high temperature conditioning and extensive bake-out, ensure high reliability and clean operation. An all metal UHV valve allows to separate the  external gas supply system from the UHV injector unit. The TGI is compatibility to standard UHV and MBE applications.

Close-up view gas connector side

Gas connector side with all metal valve and pneumatic valves.

Various customer specified  gas connectors like VCR,   DN16CF, Swagelock, KF or other interfaces are provided. We also offer complete gas cabinet solutions as shown in the figure below.


Gas Injection Systems

We offer complete Gas Injection systems with customer specific design. The Gas Injection system is usually built up in a cabinet as for example shown on the right. Turbo molecular pumping and throughout gas line heating as well as mass-flow controlling, pneumatic valve operation, purification etc. are included. The gas lines and the all metal valves are typically bake-able up to 180°C.

Gas cabinet
Gas cabinet with gas reservoir, purifies, mass-flow controllers, valves, heated gas-lines, pumping and control system.


Application

A typical applications for the TGI are listed in the table below.  An example is the injection of NH3 for ammonium based growth of nitrides, or the injection of O2 for the growth of oxides.

The TGI is also well suited for in-situ etching applications using AsBr3 , Cl2 , HCl or Br2. The typical operation pressure is about 1x10-5   mbar.


Element Application Precursor
TGI standard version (TGI):
Al MBE growth of III-V and GaN DMEAAl
As n-doping SiGe AsH3 in H2
B p-doping SiGe B2H6 in H2
Br etching of GaAs AsBr3
C SiC growth SiH3CH3 in H2
Cl etching of GaAs HCl, AsCl3, Cl2
Ga MBE growth of III-V and GaN TEGa
In MBE growth of III-V and GaN TMIn
Mg p-doping of Nitrides CP2Mg
O growth of Oxides O2 or O3
P n-doping SiGe PH3 in H2
Si MBE growth of SiGe SiH4 or Si2H6
Si n-doping III-V SiBr4
TGI version with cracker (TGI-C):
As MBE growth of Arsenides AsH3 or TBAs
N MBE growth of Nitrides NH3
P MBE growth of Phosphides PH3 or TBP


MBE System Compatibility

The TGI is compatible with most MBE systems worldwide, e.g. Riber, Oxford Instruments/VG Semicon, Varian, Eiko, DCA, Veeco/ Applied Epi and Omicron. By specifying the system type or cell model number, we can supply a fully compatible TGI for your system.

For other systems please specify mounting flange, in vacuum length, in vacuum diameter, substrate size and the distance from cell orifice to the substrate.

Downward looking or horizontal operation is possible. If you want a special design for your specific needs, please contact us for more information. A sketch with the definition of dimensions is shown in the figure below.

 

Gas conductor tubeing and connectors

Different types of gas line connectors are available: DN16CF flange, VCR, Swagelock and others on request. Please specify the gas connector.

The standard gas conductor tube material is tantalum. For special requirements other materials like PBN, Al2O3, quartz, molybdenum and PG are available. Please specify the gas conductor material on your order.

 

Cracking zone, Cooling Shroud and Shutter

An integrated high temperature cracking zone is offered as an option. A water cooling shroud is recommended for high temperature operation especially for thermal cracking option. Generally the gas injector is operated by a leak valve or pneumatic switching valve from the gas supply system. Therefore an integrated

shutter is not needed, but available optionally e.g. for very rapid gas flow interruptions.

Cracker
Cooling Shroud
Shutter
C = thermal cracking zone
K = integrated water cooling shroud
S = integrated shutter


Power Supply, Temperature Control and Cables

We provide DC power supplies and PID controllers for the TGI. The power supplies are compatible with most common AC supplies (Europe, China, Japan, USA, etc.).

For information on power supplies and temperature controllers please ask. We provide as standard a 20A cable set, including 6m power cable 2x2,5 mm² (bakeable 170°C) and 6m TC extension cable - type C (bakeable 250°C), ready-to-connect. We also offer high-temperature bake-able tapes (up to 400°C) with special lengths on request.

Technical Data

Filament type Ta or Mo filament in PBN support rings
Gas line Ta, PBN, Al2O3, Quartz, Mo and PG; other materials on request
Thermocouple Chromel/Alumel (type K), optional W5%Re/W26%Re (type C)
Bakeout temperature 250°C
Operating temperature 100-400°C
Outgassing temperature
700°C
Gas connector
DN16CF flange, VCR, Swagelock; others on request
Options integrated thermal cracking zone (C)
integrated water cooling shroud (K),
integrated shutter (S)

Dimensions

Schematic drawing TGI Schematic drawing of the Thermal Gas Injector TGI

(drawing shows TGI 40)

Specific data

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

images/header_cracking_zone.gifimages/header_cooling.gif
[mm] / [mm] [W] / [A] Product code
TGI 40 C- K- S**- LxxxD35 cell: 25/ 2.5

cell: PS 15-10
cracking zone: PS 70-10
TGI 63 C- K- S**- LxxxD35 cell: 25/ 2.5

cell: PS 15-10
cracking zone: PS 70-10
* specify sample diameter and source-to-sample distance for aperture diameter
**  rotary shutter possible on same flange
*** specify UHV length L with order

Product  code:

e.g. TGI 40-C-K-L250D35

 

is a thermal gas injector on DN40 CF flange with integrated thermal cracking zone, water cooling shroud, in-vacuum length 250 mm and a diameter of 35 mm.