Generality of the active packaging principle transcends microwave transistor applications. The new degree of freedom in manufacturing -- lithography on opposite sides of a thin film -- permits the implementation of a variety of new devices and functions. To indicate the scope of contemplated applications, let us note that the technique makes feasible an active directional coupler in which two edge-emitting laser resonators overlap in a portion of their length. It also simplifies many schemes for integrating electronic and photonic devices into a single functional unit to be placed within the integrated circuitry on a silicon chip. Thus, integration of vertical cavity surface emitting lasers (VCSEL) will enable interchip communication directly from the chip interior. Active packaging technology offers several advantages in the integration of VCSELs with silicon VLSI. For example, it allows to use non-epitaxial Bragg mirrors (such as stacks of ZnS and SiO2 layers) not only for the top but also for the bottom mirror of a VCSEL cavity. Also it permits the implementation of tandem systems in which one VCSEL (master) works under electrical injection of carriers while the other (slave) is optically pumped by the former.
Applications of compound semiconductor electronics will be associated with its use in silicon electronics. In terms of the old debate on Si vs GaAs, our view is that silicon is the ultimate customer for GaAs. The logic of industrial evolution will motivate new paths for a qualitative improvement of system components, other than the traditional path of a steady reduction in fine-line feature size.
Hybrid semiconductor systems have been central to my research for many years:
As early as 1984 [ Luryi and Sze (1984) ] suggested heteroepitaxy as the ``packaging'' technology for combination of dissimilar materials with silicon IC's on a single Si substrate [ see also Luryi and Sze 1988) ]. However, progress in heteroepitaxial growth of compound III-V semiconductors on Si substrates has been less rapid than anticipated, and genuine packaging techniques have become a viable and perhaps even preferred alternative.
Return to the first section [ Active Packaging - Philosophy ]
Return to the second section [ Active Packaging - Introduction ]
Return to the third section [ Active Packaging - HBT Process ]
Return to the fourth (preceding) section [ Active Packaging - Advantages ]
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