A team of LESA faculty and graduate students from Rensselaer Polytechnic Institute and University of New Mexico (UNM) were recently awarded U. S. Patent 9,520,472 for “Growth of Cubic Crystalline Phase Structure on Silicon Substrates and Devices comprising the Cubic Crystalline Phase.” This patent was issued on December 13, 2016 and included principal investigator Steven R. J. Brueck and inventors Sueng-Chang Lee (UNM), Christian Wetzel, Theeradetch Detchprohm (LESA/RPI), and Christoph Stark (LESA/RPI Graduate). The universities are partners in the Center for Lighting Enabled Systems & Applications (LESA) headquartered at Rensselaer Polytechnic Institute in Troy, NY.
Cubic gallium nitride (GaN) devices hold promise for addressing two long-standing issues that limit the performance of Light Emitting Diodes (LEDs). Poor performance at longer emission wavelengths known as the green gap problem; and poor performance at higher operating current, known as efficiency droop.
GaN crystals can be grown with either cubic or hexagonal (also known as wurtzite) phases. All commercial GaN LEDs are based on hexagonal materials, typically grown on sapphire substrates. “The hexagonal phase typically forms most easily, as it is the lowest energy crystallographic structure. Previous attempts to grow cubic GaN crystal structures have produced poor quality, heavily defected mixed phase materials”, said Prof. Christian Wetzel, Professor of Physics, Applied Physics and Astronomy, and co-inventor of this patent. Prof Wetzel and Prof Steve Brueck are both recognized leaders in the research and development of LED-based solid-state lighting.