200-nm InGaAs/InP type I DHBT employing a dual-sidewall emitter process demonstrating ƒmax ≫ 800 GHz and ƒτ = 360 GHz

Type I InP/InGaAs/InP double heterojunction bipolar transistors were fabricated using a simple mesa structure, where emitter junction widths have been scaled from 250 nm to 200 nm. These devices exhibit
f

_max
in excess of 800 GHz, and
f

_tau
= 360 GHz. Greater than fifty percent device yield was obtained by employing two 25 nm SiN
_x
sidewalls to protect and anchor the refractory metal emitter contact to the emitter semiconductor. A hybrid dry and wet etch process is used to form a vertical emitter mesa, causing reductions in both the emitter-base gap resistance R
_gap
and the spreading resistance beneath the emitter R
_b,spread
, leading to an expected and observed increase in
f

_max
. Peak HBT current gains beta ap 21-33, BV
_ceo
~ 4 V, BV
_cbo
~ 5 V, and J
_e
at low V
_cb
is over 10 mA/mum
²
.