Vertical III-V Semiconductor Devices

Sammanfattning: This thesis is based on three projects that deal with vertical III-V semiconductor devices. The work spans over basic research as well as more applied aspects of III-V semiconductor technology. All projects have in common that they rely on advanced epitaxial growth to form the starting material for device fabrication.In chapter two, zero-dimensional Quantum Dots (QDs) are incorporated into electronic devices to form resonant tunneling diodes. Single QDs, that can be viewed as artificial atoms, as well as coupled quantum dots, that can be viewed as artificial molecules, are investigated. Resonant tunneling diodes with a peak-to-valley-ratio of over 1000 at T=4K were fabricated and attempts were made to use the devices as spectrometers for terahertz radiation.In chapter three, InAs nanowires are used for fabrication of wrap-gated Field Effect Transistors (FETs). The combination of bottom-up fabricated, position controlled, InAs nanowires, and a processing scheme where the transistors are fabricated using a matrix of vertical wires, introduce a new type of device. High electron mobility and good current saturation is measured.Finally, in the fourth chapter, Heterostructure Barrier Varactor (HBV) diodes are fabricated and mounted in a frequency multiplier circuit. HBV diodes consist of a series of semiconductor layers where a high-bandgap material is sandwiched between layers of lower bandgap material. This results in a device with a non-linear differential capacitance that can create harmonics of an input signal. In this work a frequency quintupler (x5) from 20 GHz to 100 GHz is demonstrated, and a record conversion efficiency of 11.4% is achieved.

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