Figure 1. InP-heterojunction bipolar transistors form the 40 Gb/s multiplexer. (Heinz Jaeckel, ETH)
Processing optical signals at terahertz rates requires both the development of basic optical logic capabilities and minimization of device dimensions down to the scale of the wavelength of light. Heinz Jaeckel of the Swiss Institute of Technology (ETH; Zurich, Switzerland) and his group have demonstrated a heterojunction bipolar transistor that operates at 70 Gb/s; their long-term goal is 160 Gb/s. Jaeckel hopes to enable all-optical signal processing by developing real devices that could be incorporated into all-optical systems.
New materials and processing capabilities are fundamental to the development of such devices. Carrier lifetimes are too long in current materials to achieve the high speeds required for all-optical signal processing. Getting devices into submillimeter dimensions requires new photonic band-gap technology development, and extending performance to terabit rates will drive the fabrication techniques for advanced integrated devices.
Jaeckel's group is pursuing the technology, design, and characterization of advanced ultrafast transistors and electronic circuits as well as optoelectronic devices based on indium-phosphide (InP) technology (see figure). These devices require fabrication capabilities in the deep submicron to subnanometer range and advanced processing techniques.
All of this requires state-of-the-art semiconductor fabrication facilities and participation from a broadly based group of technologists and industrial partners. The ETH recently opened such a facility, called the Frontiers in Research: Space and Time (FIRST) lab. Six professors and about 40 researchers make up the core team to open the lab, which is a technology and fabrication facility focusing on micro- and nanotechnologies in the areas of III-IV semiconductors and silicon. Common research focuses include compound semiconductors and new materials; silicon for micro- and nanomechanics and microsensors; nanostructuring of materials and surfaces; electronic and photonic devices, circuits, ICs, and advanced packaging. Specific projects focus on areas such as vertical-cavity surface-emitting lasers, nanoscale devices, silicon micromachines, quantum transport devices, quantum dots, mode-locked lasers, and all-optical switching.
The basis of next-generation high-technology industries will be novel devices capable of faster operation and higher densities. Objects will be measured in fractions of microns with processes taking place on femtosecond time scales. Professors involved in the lab have industrial partners, and the focus is on early-phase device developments that are difficult to achieve in most industrial laboratories. Jaeckel's group has developed a 70 Gb/s PIN photodiode photoreceiver with such a partner. Going to the extremes of small size and high speeds in development labs such as FIRST today leads to the new discoveries that drive industry tomorrow.