The frequencies and dampings of the zone-center optical phonons E2 and A1(LO) in wurtzite-type GaN and AlN layers have been measured by Raman spectroscopy in the temperature range from 85 to 760 K. The GaN layer was grown by metalorganic vapor phase epitaxy and the AlN layer by molecular beam epitaxy both on sapphire substrate. The experimentally obtained frequencies and dampings are modeled by a theory taking into account the thermal expansion of the lattice, a symmetric decay of the optical phonons into two and three phonons of lower energy, and the strain in the layers induced by the different thermal expansion coefficients of layer and substrate. The results were used to determine the local temperature of a GaN pn diode in dependence on the applied voltage.
The use of cameras within mobile devices such as cellular phones as well as for automotive and other applications, is spurring innovations in pixel density, lens quality and power usage. As the performance of the camera modules improves, the requirements for more accurate assembly techniques increase as well. Within the production process, joining methods as well as manufacturing machines have to fit together. A new technological solution was therefore created that advances the accuracy of this alignment process of camera modules and results in increased performance and yield
Traditional Methods for Camera Module AssemblyCamera modules consist of two primary components: a CMOS camera sensor on a circuit board and an optically aligned and attached lens barrel assembly. Traditionally the manufacturing process inserts a threaded lens barrel into the camera housing, with the operator threading the lens barrel into the housing while monitoring the camera image on a video screen to align the lens for optimal image quality. With this type of design, the manufacturer only performs alignment of the lens assembly to the sensor in one dimension-along the optical (z) axis. For new generations of camera modules, alignment of the other two linear and additional two rotational axes becomes critical. Achieving a sharp image over the full plane of the sensor and throughout the full range of zoom capability requires accurate alignment of the lens to the sensor in not just one, but five degrees of freedom. This technology becomes essential as both camera-module resolutions and end customer expectations of image quality increase.
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