Sub-300 nm InGaAs/InP Type-I DHBTs with a 150 nm collector, 30 nm base demonstrating 755 GHz fmax and 416 GHz fT

We report InP/InGaAs/InP double heterojunction bipolar transistors (DHBT) fabricated using a simple mesa structure. The devices employ a 30 nm highly doped InGaAs base and a 150 nm InP collector containing an InGaAs/InAlAs superlattice grade. These devices exhibit a maximum f
_max
= 755 GHz with a 416 GHz /f
_T
. This is the highest f
_max
reported for a mesa HBT. Through the use of i-line lithography, the emitter junctions have been scaled from 500-600 nm down to 250-300 nm -all while maintaining similar collector to emitter area ratios. Because of the subsequent reduction to the base spreading resistance underneath the emitter R
_b,spread
and increased radial heat flow from the narrower junction, significant increases to f
_max
and reductions in device thermal resistance θ
_JA
are expected and observed. The HBT current gain β ≈ 24-35, BV
_ceo
= 4.60 V, BV
_cbo
= 5.34 V, and the devices operate up to 20 mW / μm
²
before self-heating is observed to affect the DC characteristics.