| The AlGaN/GaN high electron mobility transistor (HEMT) has evolved tremendously in the last nine years since its first demonstration. However, before commercialization, more work is needed to improve stability, efficiency, and manufacturability. This work is focused on the development and use of selective area growth (SAG) by metalorganic chemical vapor deposition, for new device designs aimed at improving said properties. The growth of the planar AlGaN/GaN device structure is also discussed, with emphasis on the semi-insulating base-layer, and the use of Fe doping to develop a high quality semi-insulating process with improved stability.; ‘Non-planar SAG’ involves a selective etch into the HEMT structure before growth, and allows contact between regrowth and the HEMT channel, which is essential for device applications. Non-planar SAG is studied extensively in this work, with emphasis on the region of interest for devices, close to the regrowth mask. The growth evolution of GaN and AlGaN is studied, as well as AlGaN alloy composition, and impurity incorporation as a function of temperature and mask material. Due to the non-planar nature of the samples, mass-transport of material may occur during sample heat-up, which needs to be avoided for well-controlled growth in the near-mask region. Mass-transport is also explored as a growth technique of its own, with advantages in simplicity and speed, since it does not require a Ga precursor.; Several device designs, utilizing both mass-transport growth and regular non-planar SAG, are implemented, most importantly aimed at reducing the source and drain contact resistance and access resistance. Some of the designs show great potential, and may wills some further optimization have a real impact on the next generation devices. |
