Molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD) is used for fabrication of epitaxially grown Nitride materials for optical, electronic and magnetic applications as well as for basic research.
The laboratory is equipped for development and supply of optically active and magnetic materials on substrates up to 4 inch diameter. State of the art in-situ characterization tools provide high reliability and reproducibility of sample properties.
A wide range of in-situ and ex-situ characterization tools are available. A range of analyzes can be performed in the analysis chamber connected to the MBEs by UHV transfer. Analysis can be done after growth or on any externally introduced sample.
- XPS with a resolution of up to 0.85 eV or intensities of up to 25 M counts/s.
- Monochromated XPS with a resolution of up to 0.6 eV or intensities of up to 1.2 M counts/s.
- Small-spot XPS with the smallest analysis area better than 70 μm
- Fine focus ion source to etch holes with minimum sizes of 150 μm for depth resolved XPS measurements
- Auger electron spectroscopy with a resolution of 0.5 at-%
- Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM) surface analysis
Development of new materials and growth processes, supply of custom template layers or heterostructures MBE and MOCVD fabrication of epitaxially grown Nitride materials for optical, electronic and magnetic applications Development and supply of optically active and magnetic materials on substrates up to 4 inch diameter
Dr. Gerd Kunert
Position: Epitaxy laboratory manager
Research interests: ferromagnetic and antiferromagnetic nitride materials, doping, fundamentals of growth, wide bandgap optically active materials.
office: building 3, room 1-29
Dr. Katarzyna Gas
Position: Epitaxy specialist
Research interests: dilute magnetic (Ga,Mn)N
office: building 3, room 1-29
Position: PhD student
Research interests: vertical GaN transistors
office: building 3, room 1-28
Position: Master student
Research interests: Molecular beam epitaxy of AlGaN
office: building 3, room 1-28
(Project related to cooperation agreement between the Senate for Economy, Technology and Research, Berlin and the NCN, Warsaw)
The project aims to enhance the light output power of laser diodes by driving them pulsed in isothermal conditions.This way much higher currents can be used than under DC conditions. The limiting factor are capacities between a very fast switching transistor and the laser diode. the capacitances can be minimized when the wiring can be shortened with vertical transistors which are the main devices to be developed within the project. Vertical transistors based on GaN have roughly 10 times smaller output capacitances than comparable Si based devices but their development sets high demands on epitaxy and processing. The project consortium partners are the Ferdinand Braun Institute FBH Berlin, Sentech, Seen Semiconductors and the EIT+ Wroclaw Research Centre.
Molecular beam epitaxy growth of tunnel structures based on insulating ferromagnetic (Ga,Mn)N for spintronic applications
(NCN FUGA Project)
The project aims to develop the growth methods of ultrathin and homogeneous epitaxial layers of (Ga,Mn)N by molecular beam epitaxy and to fabricate quantum planar structures containing this compound and p-type and n-type doped GaN. (Ga,Mn)N is a member of a family of diluted ferromagnetic semiconductors of a great technological potential in spintronics – a new and perspective branch of faster and more efficient information processing technology which takes advantage of spin (magnetic) degrees of freedom, if appropriate methods of growth are elaborated. It is expected that developed, manufactured, and characterized structures will constitute a base, a starting point for elaboration of commercially important devices. Independently from seeking these new functionalities in layered structures efforts will be exerted towards a sizable increase of Mn concentration above the currently best of 10%. Also, to achieve ferromagnetism in higher temperatures either a concept of co-doping (arsenic for example) or in heterostructures in which natively insulating (Ga,Mn)N would be forced to accept itinerant carriers form neighboring p- or n-type GaN layers will be attempted.
A three chamber Scienta Omicron MBE cluster tool is installed. It consists of 2 PRO-100 II-N MBE systems and 1 analysis chamber including AFM, STM and XPS.
Available growth materials are: Ga, Al, In, Mn, Fe and As (valved cracker source). Furthermore Mg, Si and C are installed in doping sources. Nitrogen is provided by radio-frequency plasma sources.
The base pressure of the chambers is <1×10-10 mbar. Each chamber is equipped with a turbomolecular pump, a cryo pump and an ion getter pump including a titanium sublimation pump. The typical chamber pressure during growth is 5×10-5 mbar.
The image above shows the front view of the MBE cluster. On the left hand side you see one of the growth chambers with 12 cell ports, the RHEED gun, viewports and she shutter modules in blue. The metallic tubes connect liquid Nitrogen from the face separator at the ceiling to the MBE system. The loadlock for sample loading is depicted in the center. Behind the loadlock one can see the semi-automatic transfer chamber. On the right-hand side is the analysis chamber with the microscopy stage and the hemispherical electron energy analyser. The second growth chamber is not visible from this angle.
MBE Chamber 1 below the liquid Nitrogen phase separator. On the left hand side the pumping systems are installed: Cryo-pump below and Ion getter pump above the table. The turbomolecular pump is partially visible on the far left. The Chamber is equipped with RHEED and an EpiCurveTT AR blu optical analysis system. It provides growth temperature data, measures layer thicknesses and wafer bowing. Effusion cells are water cooled, provided through red and blue tubing below the chamber. Between the ion getter pump and the top of the chamber a quadrupole mass spectrometer is installed to analyse residual elements present in the chamber.
Metal-organic Chemical Vapour Deposition (MOCVD)
- Aixtron Closed Coupled Showerhead reactor in 3×2 inch/1×4 inch configuration, enabling true scaling to mass production. The MOCVD reactor is equipped with LayTec EpiCurveTT and a three zone heater.
- Growth temperatures of up to 1200° C can be reached. Available sources: TMGa, TEGa, TMIn, TMAl, Cp2Mg, NH3 and SiH4
Special sources like Cp2Fe, Cp2Mn and CBr4 are available on request
The above image shows the AIXTRON MOCVD reactor. The glovebox is constantly purged with Nitrogen for clean sample handling. Samples are introduced through the antechamber on the right hand side. The cabinet contains the gas system including all metal-organic source materials.
The open reactor is loaded with 3 2-inch sapphire wafers. During growth the reactor is closed and all gases are introduced through the perforated lid. The 4 larger holes in the lid are used for optical in-situ growth analysis with an EpiCurve TT AR blue system. It provides growth temperature data, curvature signals and layer thicknesses. The samples are heated by a 3-zone heater to temperatures of up to 1200°C. Toxic gases used for growth are neutralised afterwards through a dry scrubber system.
Dr. Gerd Kunert
ul. Stabłowicka 147, budynek 3 / 1-29
phone: +48 71 734 7164
Posted by Agata Kołacz, Posted on 08.10.2015