Uniform-Base InP/GaInAsSb DHBTs Exhibiting $f_{\rm MAX}/f_{\rm T}>635/420~{\rm GHz}$

Type-II InP/GaInAsSb-based double heterojunction bipolar transistors (DHBTs) with f
_MAX
=636 GHz and a simultaneous f
_T
=424 GHz were realized with a 20-nm-thick compositionally uniform quaternary GaInAsSb base and a 125-nm InP collector. The GaInAsSb alloy exhibits superior electron and hole transport properties compared with GaAsSb, resulting in improved device performance. The present transistors offer the highest f
_MAX
to date for GaInAsSb DHBTs and match the highest f
_MAX
of any Sb-based DHBT.