The III-nitride material system posesses several unique properties that sets it apart from other III-V semiconductors. Chief among these are the unique polarization properties, a result of the lower symmetry of the III-nitride wurtzite crystal structure. The large bandgap offsets potentially afforded by the system, spanning from 0.7 eV for InN up to 6.2 eV for AlN, are also of great benefit to device engineering. Progress in optoelectronic devices such as light emitting diodes and laser diodes, and in power electronic devices such as high mobility electron transistors, take full advantage of these properties by making judicious use of substrate orientiation and band offsets. Fundamental limits related to the poor p-doping properties in III-nitrides, however, often constrain the full potential of devices based on bipolar transport.

This work focuses on the growth of structures for vertical unipolar transport. Due to the large polarization sheet charges induced at nitride heterointerfaces as a result of polarization effects in heterostructures, rectifying diodes can be achieved without the use of p-GaN. This novel structure is termed a dipole induced diode. Several series of such dipole induced diodes, using different interlayer material are grown and characterized by MBE. The results indicate that the induced depletion region at the negative polarization interface in such diodes plays a large role in determining their rectifying properties. Other important differences, such as differences in tunneling versus thermionic transport mechanisms and the effects of binary versus ternary barrier material are presented. Finally, the application of these diodes to devices and as a tool to probe the higher energy bandstructure of III-nitrides will be discussed.