UC Berkeley

The group III-N alloy system has attracted considerable interest for various electronic and optoelectronic applications including high power and high frequency electronics, photovoltaics, photoelectrochemical electrodes, and solid-state light emitters. While wide-gap group III-N materials have achieved commercial success and technological maturity, more narrow-gap alloys closer to the InN end of the system have yet to make an impact. The unique defect properties of InN, mostly stemming from an unusually large electron affinity, have masked even the most basic electronic and optical properties and made technological advancement difficult. This dissertation builds upon the collective work of the small InN community that has been slowly building up fundamental understanding of this material over the last decade.

The development of thermopower measurements as a tool for investigating the transport properties of InN is a recurring theme in this work. Thermopower measurements of Mg-doped InN provide some of the first definitive proof of free-hole conduction and help to elucidate the role of Mg as an acceptor. Analysis of multilayer structures using a parallel conduction model allows measurement of two of the most fundamental p-type transport properties, free-hole concentration and mobility, which have been difficult to evaluate by other techniques. Well developed transport modeling theories are extended to include the effects of donor-type, charged dislocation scattering on electron mobility and thermopower in n-type InN. Comparison of this modeling to variable temperature transport data and electron microscopy has provided strong evidence that the high density of dislocations in InN are positively charged donors and can limit the electron mobility in n-type InN. Finally, electrolyte gating is shown to be a powerful tool for controlling the surface band bending condition. Using this technique, parasitic surface currents are eliminated leading to the first measurement of rectification in InN, a crucial step on the path towards InN device development.