Heterostructure Field Effect Transistors and Millimeter Wave Integrated Circuits

Doktorsavhandling, 1995

This thesis deals with the research and development of HFETs and HFET based circuits. One of the main aims of the work presented in this thesis has been to develop processes to fabricate state of the art devices and circuits. The process development has been directed on simplicity, and the processes have been developed until they are adequate for the needs. HFETs have been developed on different types of III-V heterostructures. The general development of the HFETs in recent years is described. We have gone from the ordinary AlGaAs/GaAs on GaAs, via pseudomorphic AlGaAs/InGaAs on GaAs (with uniform- and .delta.-doping), arriving at today's state of the art material, lattice matched InAlAs/InGaAs on InP. Most of our structures have been designed by us and grown by some external laboratory. We have also developed more novel structures, such as materials with high indium concentration, InSb structures, and structures containing phosphide. The technology has then been used to build different types of microwave and millimeterwave circuits: amplifiers (low-noise and gain), mixers (resistive and drain), frequency multipliers (doublers), and oscillators. By having an in house technology it has been possible to try new types of circuits and circuit solutions. A well-equipped microwave and millimeter wave laboratory allows us to extensively characterize the HFETs and circuits. This characterization helps us to evaluate the HFETs and the circuits, and enables us to develop both small- and large-signal HFET models. Furthermore, we have developed a Monolithic Microwave Integrated Circuits (MMIC) technology. It was initiated when we realized the problems of designing and fabricating circuits for high frequencies (>100 GHz) using conventional hybrid technology. We have now developed the processes for the passive components and have fabricated our first MMICs. The device results include a 0.15 .my.m gate length InAlAs/InGaAs on InP HFETs with a maximum frequency of oscillation of 350 GHz and an intrinsic transit frequency of 160 GHz. The MMIC results include a 119 GHz amplifier with a gain of 6 dB and an F-band resistive HFET mixer with a conversion loss of 9 dB.