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Fig. 1 shows an example of temperature measurements at FBH during AlGaN buffer growth on GaN. After changing the pressure from 600 mbar to 60 mbar and H2 to 70%H2/30%N2, the temperature dropped. The EpiCurve TT, which measures the 950 pyro emission, showed that the pocket temperature (red curve) decreased insignificantly, whereas the GaN surface temperature measured by Pyro 400 dropped by 75 K (orange curve). This difference could not have been detected without Pyro 400.
The study proved that the wafer surface temperature is affected by changes of pressure and gas phase much stronger than the pocket temperature. This is because the modified thermal conductivity and the thermal capacity of the gases at low reactor pressure results in an increased vertical temperature gradient between pocket and ceiling.
Mr. Hoffmann of FBH commented: „With Pyro 400 we obtain valuable information about temperature effects that are not visible to the conventional infrared pyrometers. Today, this is the best method to improve the uniformity of the surface temperature.“ Using a convex pre- bowed GaN substrate and changing the growth conditions, the active region could be deposited on nearly flat wafers with homogeneous temperature distribution.
Further reading: V. Hoffmann et. al. Uniformity of the wafer surface temperature during MOVPE growth of GaN-based laser diode structures on GaN and sapphire substrate – submitted to J. of Crystal Growth, ICMOVPE XV procedures
RFMD Introduces RF3482 Single-Chip Integrated Front End Module 2010-06-29
RF Micro Devices, a global designer and manufacturer of high-performance radio frequency components and compound semiconductor technologies, today announced the availability of the RF3482 front end module (FEM). RFMD’s highly integrated RF3482 single-chip FEM integrates a WiFi power amplifier with a single-pole, three-throw (SP3T) switch for 2.4 GHz to 2.5 Ghz ISM band applications.
By integrating the complete switch functionality, the RF3482 is able to route WiFi and Bluetooth(R) receive/transmit signals to two system-on-chip (SOC) transceivers, a typical design architecture implemented in a wide range of high-performance consumer electronics and handset/handheld WiFi applications. Additionally, the SP3T switch can act as a splitter to transmit or receive Bluetooth(R) and WLAN signals simultaneously.
The highly integrated RF3482 satisfies the need for aggressive size reductions for 802.11b/g front-end designs by realizing up to a 50% size reduction versus current discrete designs, while at the same time greatly reducing the number of components outside the core chipset. The RF3482 integrates a 2.5 GHz b/g power amplifier with 16dBm of linear output power for higher efficiency and lower EVM for 11n applications. The RF3482 also integrates 2170MHz filtering and harmonic attenuation, reducing the need for a high loss/attenuation filter at the FEM output and
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www.compoundsemiconductor.net July 2010
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