Micro-diffraction and micro-fluorescence and micro-XAS of compositional gradiented Multiple Quantum Well Electro-Absorption Modulated Lasers

In epitaxial growth different layers are sequentially deposited uniformly on the entire substrate, giving a structure with a specific function (led, laser, amplifier, modulator, photodiode, waveguide). Modern devices require high performances that may require integration of different functions on the same chip. Strong efforts are devoted to develop integration techniques such as Selective Area Growth (SAG). SAG is based on the fact that deposition doesn’t occur on semiconductor areas covered by SiO2 masks. Species impinging a mask migrate through the unmasked semiconductor where the growth can take place. This means that reactive species coming from the gas phase are enriched by those coming from the mask in its neighbouring. As the reactive species have different diffusion lengths the result is a variation in composition and thickness of semiconductors grown near (SAG region) and far (field region) from the mask (see Figure): the monolithic integration of different materials and relative functions is so obtained. This allows realizing integrated optoelectronic devices called Electro-absorption Modulated Laser (EML) i.e. an MQW-Distributed Feedback Laser (DFB) monolithically integrated with an MQW Electro Absorption Modulator (EAM). Using a 1.7 um x 5.3 um X-ray beam available at the ESRF ID22 beamline we report micro-diffraction and micro-fluorescence and micro-XAS study on MQW EML.