Fabrication Of Reduced Area Ingaas/Inp Hbt And Dhbt Devices

We have developed a fabrication procedure for reduced area InP/InGaAs based HBT and DHBT devices using a process involving both wet chemical and ICP plasma etching. Optical emission spectroscopy was used for end-point detection during plasma etching. We studied the effect of scaling down the base layer thickness as well as the device geometry on the de and microwave characteristics. A 2x4 mu m(2) device had a peak f(t) and f(max) of 160 and 155GHz, respectively. When the emitter area was reduced to 1.2x3 mu m(2) the f(t) remained about the same, around 160 to 170 GHz. However, the f(max) showed a substantial increase from 155 to 200 GHz for the DHBT and 280GHz for the HBT. This improved microwave performance is due to reduced parasitics, such as C-bc. The 1.2x3 mu m(2) devices are attractive for high-speed circuit applications, since the microwave performance peaked at 5mA, as opposed to 10mA for the 2x4 mu m(2) device. Furthermore, the f(t) and f(max) of the DHBT device were both above 150 GHz at 3mA, which is a desirable operating current for a circuit.