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The CSRL provides rapid prototyping for both microelectronic and
optoelectronic integrated circuits. These circuits include those in which a
single technology integrates many similar devices onto one chip as well as
those in which multiple technologies are themselves integrated into one chip.
Our full suite of device and circuit fabrication technologies enable such
monolithic integration with a flexibility and yield unavailable in universities
or in industry. For example, CSRL researchers are working to integrate
optoelectronic devices such as Vertical-Cavity Surface-Emitting Lasers
(VCSELs) with electronic devices such as HBTs to form true optoelectronic
integrated circuits (OEICs).
Microelectronic integrated circuit technologies
include:
- Long wavelength, low-power photoreceivers based on heterojunction bipolar
transistors (HBTs) and p-i-n detectors in the InGaAs/InP material system
- High-speed, low-power digital circuits based on complementary
heterojunction field-effect transistors (CHFETs) with self-aligned refractory
gates
- Monolithic microwave integrated circuits (MMICs) based on strained quantum
well field-effect transistors (SQWFETs)
Those technologies in turn are based on the
following processes:
For HBT circuits:
- Self-aligned fabrication technology for micron-scale emitter widths
- Multi-level metal interconnects with highly planar inter-level
dielectrics
- Tantalum nitride resistors and tantalum oxide capacitors with excellent
temperature stability
For CHFET digital circuits:
- High-performance epitaxial strained quantum well p-channel junction
field-effect transistors (JFETs)
- All-implanted n-channel JFET
- Multi-level metal interconnects with silicon nitride inter-level
dielectric
For MMIC prototypes:
- Sub-micron gate technology
- 50-µm and l00-µm wafer backside via hole processing
- Silicon nitride capacitors with airbridge interconnects and tantalum
nitride resistors
Photonic integrated circuit technologies and
processes include:
Photonic integrated circuit (PIC) prototype processing is based largely on
reactive ion beam etching (RIBE) to fabricate vertical sidewall mesa structures
with optically smooth sidewall morphologies. These properties are critical to
minimizing scattering loss in passive and active photonic structures. PIC
fabrication includes the following
technologies and processes:
- High-performance GaAs/AlGaAs Mach-Zehnder interferometers. These devices
incorporate many component technologies for general PIC fabrication, including
waveguides, power splitters, modulators, and power combiners. For example, a
new X-Y coupler has been developed with improved on/off extinction ratios and
normal- and inverted-output ports that offers opportunities for optical logic
functions.
- Electro-optical phase modulators. These modulators in the GaAs/AlGaAs
material system provide improvements in size, weight, and power
characteristics. They greatly exceed the performance of those based on existing
lithium niobate modulator technology.
- General PIC packaging and systems integration. A major problem that limits
PIC commercialization is packaging and coupling PICs to optical fibers. One
novel CSRL solution is a detuned, second-order grating that greatly improves
input and output coupling. CSRL scientists are incorporating these and other
techniques into PIC
packages to enhance manufacturability.
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