Fabrication, characterisation and modelling of heterojunction bipolar transistors and resonant tunnelling diodes based on indium phosphide

The ever increasing demand for higher power devices at higher frequencies has prompted much research recently into the InGaAs/InP material system; this thesis describes two alternative devices (based on InGaAs/InP) that can be employed into THz-oscillator circuits: the hetero-junction bipolar transistor and the resonant tunnelling diode. The challenges of designing with those devices includes several aspects that span from the simple fabrication scaling eort to the physics of the device and its intrinsic properties. For these reasons a deep understanding of the devices is an essential prerequisite for future applications such as oscillator design. In this work, HBTs and RTDs were fabricated with standard photolithographic techniques: the minimum features reached were 3x3 m2 for metal deposition and 2 m for gaps between objects. In spite of their good DCtoRF conversion rate ( 36%), HBTs main disadvantage is connected to their fabrication: their performances (fT and fmax) strongly depends on the dimensions of contacts and distances between terminals. Medium{scaled devices (emitter area 10x10 m2) reached an fmax of 5 GHz RTDs, on the other side, have a lower DCtoRF gure (theoretical 20%, practical 2%) but their performance and mainly determined by their peculiar layer structure more than their dimensions. Fabricated RTDs showed a PVCR of 110KA/cm2 with a PVCR of 1.5. These gures are quite promising for THz{oscillator production: recent work produced GHz- sources (17.5 GHz with an output power of 21.83 dBm) with similar devices