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Fiber Optic Tutorials

 

What are Vapor-Phase Epitaxy (VPE) and Metal-Organic Vapor-Phase Epitaxy (MOVPE)?

This is a continuation from the previous tutorial - what is liquid-phase epitaxy (LPE)?   Vapor-Phase Epitaxy In vapor-phase epitaxy (VPE), the source chemicals from which the epitaxial layers are gown are gaseous. The technique has been widely used for the growth of several III-V compound semiconductors. VPE is often classified as one of two different methods, the chloride and the hydride techniques. In the chloride method, \(\text{AsCl}_3\) or \(\text{PCl}_3\) is passed over elmental \(\text{Ga}\) or \(\text{In}\) to form metal chlorides. These metal chlorides then react with \(\text{AsH}_3\) or \(\text{PH}_3\) near the \(\text{InP}\) substrate to form epitaxial layers of \(\text{InGaAsP}\)...

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What is Liquid-Phase Epitaxy (LPE)?

This is a continuation from the previous tutorial - temperature dependence of threshold current of semiconductor lasers.   The lattice-matched crystalline growth of one semiconductor over another is called epitaxy. The development of sophisticated epitaxial techniques has been of major significance in the development of high-quality, reliable semiconductor lasers. The commonly used techniques are liquid-phase epitaxy (LPE), vapor-phase epitaxy (VPE), and molecular-beam epitaxy (MBE). In LPE a saturated solution of the constituents of the layer to be grown is cooled while in contact with the substrate. In VPE, the epitaxial layer is grown by the reaction of gaseous elements or...

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Temperature Dependence of Threshold Current of Semiconductor Lasers

This is a continuation from the previous tutorial - how to estimate the threshold current density of a semiconductor laser.   In this tutorial we address the important issue of the high-temperature performance of semiconductor lasers. The threshold current of double-heterostructure lasers is found to vary with temperature \(T\) as \[\tag{3-6-1}I_\text{th}(T)=I_0\exp(T/T_0)\] where \(I_0\) is a constant and \(T_0\) is a characteristic temperature often used to express the temperature sensitivity of threshold current. For AlGaAs lasers the observed \(T_0\ge120\text{ K}\) near room temperature, while for InGaAsP lasers, \(T_0\) values lie in the range of \(50-70\text{ K}\). A lower \(T_0\) value implies...

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How to estimate the threshold current density of a semiconductor laser?

This is a continuation from the previous tutorial - experimental results of radiative and Auger recombination coefficients of semiconductor lasers.   In this tutorial we show how the calculations presented in the radiative recombination in semiconductors tutorial and the nonradiative recombination in semiconductors tutorial can be used for estimating the threshold current density \(J_\text{th}\) of a semiconductor laser. Because of the different facet reflectivities for the TE and TM modes, the TE mode generally has a lower threshold. In the emission characteristics of semiconductor lasers tutorial we obtained \(J_\text{th}\) using the linear-gain model based on Equation (2-4-3) [refer to the...

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Experimental Results of Radiative and Auger Recombination Coefficients in Semiconductor Lasers

This is a continuation from the previous tutorial - nonradiative recombination in semiconductors.   In this tutorial we present the experimental results on the measurement of radiative and Auger coefficients (the parameters \(B\) and \(C\)) [refer to Equation (2-4-9) in the gain and stimulated emission in semiconductor lasers tutorial] for InGaAsP material. Many of these measurement were made in an effort to understand the observed higher temperature dependence of the threshold current of InGaAsP lasers (\(\lambda\approx1.3\) μm and 1.55 μm) compared with that of AlGaAs lasers (\(\lambda\approx0.82\) μm). Measurements under conditions of both optical and electrical excitations have been reported....

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