NSF Award
0711847
This Small Business Innovation Research Phase I Project proposes to develop a new epitaxial growth process for production of long-lasting (lifetime > 20,000 hours), high-efficiency (wall-plug efficiency > 10%) deep ultraviolet light emitting diodes (DUV LEDs) based on III-Nitride materials. Due to the lack of native substrates DUV LEDs are made from heteroepitaxial AlInGaN or AlGaN films grown on sapphire substrates and suffer from a high density of crystal defects. Large concentration of growth defects reduces DUV LEDs' efficiency, reliability and lifetime. Previous experience reveals that crystal defects can be reduced in thick films due to defects annihilation and strain-relaxation. <br/><br/>The goal of the research is the development of a new process to facilitate the growth of thick III-Nitride materials and as a consequence allow for material relaxation and defects annihilation. The high growth rate will be achieved by using stable precursors that do not have strong gaseous phase reaction, as opposed to metal organic precursors. The PI proposes also to modify the Hybrid Precursor Vapor Phase Epitaxy (HPVPE) shower head and gas delivery system that has been used with the metal organic gases. The grown materials and the LEDs built will be characterized and evaluated to optimize the proposed process. The technical prospects of the proposal are promising, since growth of thick layers is expected to result in the annihilation of dislocations. <br/><br/>The proposed activity will advance the knowledge and understanding of the growth of high quality materials and devices, which are normally difficult to grow. This aspect of the work is expected to benefit technologies other than LEDs.
