Development of 4 inch Semi-Insulating Gallium Nitride Substrates

High-performance GaN-based devices, such as microwave transistors, laser diodes and light emitting diodes have been demonstrated on sapphire and silicon carbide substrates. Gallium nitride substrates are expected to further improve the performance of these devices due to close lattice and thermal expansion match with GaN-based device structures. The development of a low defect density semi insulating GaN substrate will result in improved properties of epitaxial GaN films, and subsequently will improve the performance of GaN-based devices. Moving to wafer sizes larger than 2" will also create lower cost opportunities through process scaling. This Phase I SBIR will develop 4" diameter semi insulating GaN substrates using a large area hydride vapor phase epitaxy (HVPE) system. Hydride vapor phase epitaxy has gained attention as a technique to grow high quality, free-standing bulk GaN materials for use as substrates. The HVPE technique has the advantages of a high growth rate (up to 0.5 mm/hr), relatively low cost, and demonstrated low defect densities (105 cm-2). In Phase II of this proposal we will complete GaN HVPE growth studies and proceed to develop low defect density 4" GaN substrates for commercialization.