Next-generation HBT wafers

improve reliability and ease of use

Kopin (Taunton, MA), a supplier of heterojunction bipolar transistor
(HBT) wafers, has announced a new HBT technology, based on indium gallium
phosphide (InGaP), that promises better reliability for high-current high-frequency
telecom applications. InGaP HBT devices offer the high efficiency and linearity
associated with existing AlGaAs HBT devices, but are easier to process
and capable of operating under a wider range of power and temperature conditions.

Currently, AlGaAs HBT wafers are finding use in cellular phone and fiber-optic
applications, where HBT devices perform power amplification. However, the
greater flexibility of InGaP could push HBT technology into a host of new
applications.

InGaP technology simplifies the formation of circuits, allowing circuit
manufacturers to precisely etch emitter layers. The full HBT device is
incorporated within the wafer's layer structures.

InGaP HBT wafers, which incorporate the full HBT device within their

layer structures, simplify the formation of circuits by allowing circuit

manufacturers to precisely etch emitter layers.

After conducting reliability tests on components fabricated with InGaP
HBT wafers, Sharp (Tenri, Nara, Japan), a manufacturer of telecom ICs,
found no device degradation after 10,000 hours of rigorous accelerated
testing. Test conditions included a junction temperature of 264°C,
a current density of 25,000 A/cm² , and an operating voltage
of 2 V.

InGaP HBT components were also subjected to RF testing conducted at
the University of Illinois. Dr. Greg Stillman, a professor of electrical
engineering at the university, says that the tests showed that the bandgap
structure of these devices provides greater temperature stability and reliability
than the older AlGaAs HBT technology. According to Dr. Stillman, the newer
devices are suitable for A/D converters, oscillators, and power amplifiers
that will be used in higher-frequency wireless, digital radar, collision
avoidance, and satellite systems.

InGaP HBT wafers are currently available in large quantities, at prices
similar to Kopin's AlGaAs HBT products. For more information, contact Matt
Micci of Kopin at 508-824-6696 or visit http://www.kopin.com.