proven to operate quite well at liquid helium temperatures and in magnetic fields up to 9 T. In the 8500 Series THz system, fiber-coupled THz source and detector are mounted within the cryogenic environment and in proximity to the sample. Custom designed optical stages maintain good optical alignment of the THz devices over temperature and multiple thermal cycles.
The Lake Shore system uses CW measurements to enable variable temperature measurements of electronic and magnetic materials in two distinct sample types — semiconducting wafers (like InSb or InP) and thin conductive films supported by an insulating substrate (like ZnO/sapphire, graphene on silicon, or 2DEGs).
By replacing terahertz time domain technology with less costly, higher resolution CW spectroscopy, instrumentation cost can be reduced by 50 to 75%, opening the technology to a much broader market. What’s more, these capabilities are provided in a completely integrated platform that has the software to conduct proceduralized experimental methods and reliably analyse the spectral results.
LayTec Pyro 400 Gen2
Pyro 400 Gen2 is a unique optical metrology system for in-situ measurement of the GaN-wafer temperature during LED-structure growth in MOCVD. Pyro 400 Gen2 uses 400nm pyrometry to measure the temperature of the GaN buffer. It can be integrated into the control loop for the growth temperature of the MOCVD system and allows precise control of the wafer temperature during the critical growth steps of an LED structure:
The growth of the multi quantum wells. Pyro 400 Gen2 uses a robust state-of- the-art PLC based measurement scheme and is designed for 24/7 use in LED production. In addition to earlier LayTec
calibrated with LayTec’s patented AbsoluT 400 calibration device. Pyro 400 Gen2 is the first and only 400nm pyrometer on the market to perform emissivity correction pyrometry.
Besides the thermal emission from the wafer, the reflectance is also measured, allowing for real-time emissivity measurement. An established technique for IR-pyrometers, emissivity correction has never been implemented in the blue/ near-UV spectral range before.
Pyro 400 generations it offers as a unique feature: real-time emissivity correction to compensate for emissivity changes that occur during the growth of different materials.
Pyro 400 Gen2 is controlled and operated by LayTec’s EpiNet software. It is also fully integrated into LayTec’s fabwide visualization software that allows easy stop-or-go decisions for operators based on traffic lights. Part of the Pyro 400 Gen2 package is the unique calibration tool AbsoluT 400 that allows for an easy but very precise calibration of the Pyro 400 Gen2.
Therefore not only wafer-to-wafer and run-to-run variations can be detected and controlled, but also the very important tool-to-tool variations. Pyro 400 Gen2 can be applied to a wide range of MOCVD systems.
Pyro 400 Gen2 solves the challenge of measuring and controlling wafer surface temperatures during the growth of GaN LED-structures on sapphire, even when AlGaN layers or superlattices for better carrier confinement or electron blocking are introduced. Such layers produce changes in the emissivity of the growing layers, directly affecting the measured surface temperature.
Earlier versions of 400nm pyrometers were unable to account for emissivity changes and have failed to correctly measure the surface temperature on these structures. Pyro 400 Gen2 also solves the challenge of tool-matching, because the pyrometer can be easily
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www.compoundsemiconductor.net March 2014
The main challenge has been providing a reflectance measurement spectroscopically fitting the black body emission. The emission from the same light source integrated in a regulated device (AbsoluT 400) emulates the emission of a black body at a given temperature and allows for a precise calibration.
Tektronix, Inc
PA1000 Single-phase Power Analyser
New semiconductor technologies such as GaN (gallium nitride) and SiC (silicon carbide) are emerging to meet the greater demands of today. To meet these requirements, new test and measurement tools are needed to keep pace. Last year Tektronix expanded its family of precision power analysers with the introduction of the PA1000 single-phase power analyser.
Featuring a patent pending Spiral Shunt design, the PA1000 provides engineers designing and testing power supplies, consumer electronics and other electrical products with accurate power measurements in the shortest possible time.
Features such as a colour graphical display, one-button application modes and intuitive menu system enable optimum instrument set up in seconds, and the powerful PWRVIEW PC software includes comprehensive reporting features such as a full compliance
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