Monolithic Integration
Generic benefit s of monolithic integration are commonly known from silicon ICs, which have experienced a continuous, intense Technological and economic development over several decades. As a consequence, the development of monolithic optoelectronic ICs (
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Monolithic Integration
Herbert Venghaus, Heinz-Gunter Bach, Frank Fidorra, Helmut Heidrich, Ronald Kaiser, and Carl Michael Weinert
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Introductory Remarks
Generic benefits of monolithic integration are commonly known from silicon ICs, which have experienced a continuous, intense technological and economic development over several decades. As a consequence, the development of monolithic optoelectronic ICs (OEICs) has been considered equally rewarding for quite a while 1 . However, there is a fundamental difference between purely electronic and optoelectonic (OE) integration: Si-integration is essentially the engineering of electrical functionalities by incorporation of dopants into the host material, the key element is the transistor, and a single chip may contain millions of transistors. On the other hand, OE integration requires the epitaxial growth of materials, which have different compositions and thus exhibit different energy gaps and different refractive indices. OE integration further includes vertical and lateral structuring, and one can achieve optical, optoelectronic and electronic functionalities as well. The key component is the semiconductor laser, and in contrast to Si-integration, the components to be integrated on a single OE chip, are rather different. In comparison to Siintegration, OE integration is considerably more complex by its very nature and OE subcomponents have significantly larger geometrical dimensions than integrated (Si-) transistors. Thus the number of different subcomponents to be integrated on a single OE chip is fairly limited (several tens at most, and frequently only a few). OE modules can be implemented in many different fashions ranging from hybrid over partly integrated to monolithically integrated (see also Chap. 10). According to their complex functionality most modules in optical communication systems are very likely to be, even in the long run, hybrid ones, in the sense that monolithic OEICs are combined with other elements based on Si0 2 /Si, LiNb0 3 , glass, polymers or Si, for example, as outlined in the preceding chapter. In agreement with such expectations the goal of monolithic 1 The term OEIC refers to the integration of optoelectronic devices such as lasers and detectors with electronic ones, transistors for example. The frequently used term Photonic Integrated Circuits (PICs) designates a subset of OEICs, namely optically interconnected guided-wave optoelectronic devices.
N. Grote et al. (eds.), Fibre Optic Communication Devices © Springer-Verlag Berlin Heidelberg 2001
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Monolithic Integration
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OE integration is to (1) integrate an optimum number of different components on a single chip and (2) take care of enabling an efficient hybrid coupling with complementary optoelectronic and electronic chips. A significant part of the optoelectronic module cost is due to mounting and packaging. Monolithic integration lowers the mounting and packaging cost by a reduction of cost-driving alignment and fixing procedures. Even the mounting and packaging costs
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