In/sub 0.53/Ga/sub 0.47/As/InP type-I DHBTs having 450 GHz f/sub T/ and GHz f/sub max/ w/C/sub cb/I/sub c/ = 0.38 ps/V
The paper reports on InP/In<sub>0.53</sub>Ga<sub>0.47</sub>As /InP DHBTs fabricated using a conventional mesa structure, exhibiting a 450 GHz f<sub>tau</sub> and 490 GHz f<sub>max</sub>, which is to our knowledge the highest simultaneous f<sub>tau</sub> and f<sub>max</sub>for a mesa HBT. The collector has been scaled vertically to 120 nm for reduced electron collector transit time, aggressively scaled laterally to minimize the base-collector capacitance associated with thinner collectors, and the base and emitter contact resistances rho<sub>c</sub> have been reduced. The device reported here employs a 30 nm highly doped InGaAs base and an InGaAs/InAlAs superlattice base-collector grade