HBTs for mixed signals applications
Heterojunction Bipolar Transistor process has been developed in the
InP/InGaAs material system, and is used for the fabrication of very
high frequency mixed signals ICs
The HBT structure
comprises a strained graded gap InGaAs base and a step graded
base-collector junction. With a triple mesa process and 2 µm
wide emitter metal contact, HBTs exhibit max cut-off frequencies above
220 GHz for both Ft and Fmax, while retaining a breakdown voltage
larger than 5 V. Circuits are designed based on such HBTs, together
with thin film resistors and capacitors, and 3-layer metal
Circuits with a
transistors count of up to 100 have been fabricated, mainly intended
for 43 Gbit/s optical fiber applications. Owing to the large intrinsic
performances of the devices and to a specific design methodology and
accurate modeling, circuits have been designed and fabricated offering
state of the art results.
|Microphotograph of a 0.7 µm
emitter width InP/InGaAs HBT
|Example of a 40 Gbit/s mixed signal IC.
Besides HBTs, this circuit integrates resistors, capacitors, a 3-layer
metal interconnects, and coplanar access lines.
|Output eye diagram of a D-FF operating at 40
Gbit/s, exhibiting a
record low value of 260 fs jitter.