Processing and device issues in GaN and related compounds

Over the last decade, significant and rapid advances in the epitaxial growth of gallium nitride (GaN) and related wide bandgap materials have yielded exciting developments. Both optical and electronic devices have been demonstrated. Light emitting diodes (LEDs) and laser diodes (LDs) operating at various short wavelengths have been shown to be very reliable and are commercially available. AlGaN/GaN heterostructure field effect transistors (HFETs) demonstrating high bandwidths and record microwave powers have also been demonstrated. In spite of these advancements, there are still many issues to be resolved in terms of materials quality, processing methodologies (etching, high temperature stability of ohmic and Schottky contacts, etc), and device design and fabrication. In this talk, we will describe our work on photoelectrochemical (PEC) etching of GaN as a tool for material characterization and device fabrication. Revelations of defect structures especially edge and screw dislocations in n-GaN will be discussed. We will also describe our work on developing thermally stable ohmic and Schottky contacts, inductively-coupled- plasma reactive ion etching (ICP-RIE) for device fabrication. Lastly, results on DC, RF, CW power and microwave noise for AlGaN/GaN HFETs will be presented and discussed in the context of GaN material quality.