InP DHBT Amplifiers and Circuit Packaging up to Submillimeter-Wave Frequencies

Doktorsavhandling, 2015

This thesis treats the design and characterization of amplifiers operating up to submillimeter-wave frequencies and packaging of such circuits into waveguide modules. The circuits use an advanced indium phosphide (InP) double heterojunction bipolar transistor (DHBT) process with a multilayer back-end. Several amplifiers in the frequency range from 80 to 300 GHz with state-of-the-art performance are presented. The amplifiers utilize different transistor configurations: common-emitter, common-base, and cascode. One of the amplifiers, a five-stage common-emitter circuit, demonstrates 24 dB gain at 255 GHz with a minimum noise figure of 10.4 dB at 265 GHz. This is the lowest reported noise figure for amplifiers in bipolar technology operating at such high frequencies. Circuits like these can find applications in a variety of systems such as wireless high data-rate communication links and high-resolution imaging systems. Furthermore, amplifiers with the highest reported bandwidths for transistorbased amplifiers, regardless of transistor technology, are presented in this thesis. These amplifiers use distributed topologies to achieve such wideband characteristics. The widest bandwidth is reached with a 2-cascaded distributed amplifier that has an average gain of 16 dB from 2 to 237 GHz, i.e., a bandwidth of 235 GHz. A potential problem with integrated circuits with a large front-side metallization is the risk of resonating parasitic modes within the circuit substrate. The influence of such resonances is studied through simulations and measurements of passive and active circuits. It is shown that a resistive Si carrier underneath the circuit is an effective method to eliminate the effects of parasitic substrate modes. The high operating frequencies of these circuits make the development of a functional packaging method challenging. In this thesis, two waveguide InP DHBT amplifier modules operating in the frequency bands 150‒260 GHz and 210‒300 GHz using a novel waveguide-to-circuit transition realized in membrane technology are demonstrated. It is the first published results on InP DHBT amplifier modules operating at these high frequencies. Furthermore, membrane technology has not been used in packaging of transistor-based integrated circuits before. One of the amplifier modules is measured at a temperature of 100 K. The noise temperature of the module is reduced from 3500 K at room temperature to 1800 K when cooled. This is the first reported characterization of an InP DHBT circuit at cryogenic temperature.