Solar-blind GaN p-I-n UV Photodiodes

Photodiodes have high efficiency since the absorption region thickness is large. However, no GaN p-i-n photodiodes have been reported due to the difficulty in achieving low background doped GaN. This Phase I program seeks to determine the increase in quantum efficiency achievable by the use of a thick intrinsic layer inserted in the p-n junction to increase the absorption region thickness. In addition, we anticipate a performance advantage to growing GaN photodiodes on SiC substrates which have a closer lattice and thermal coefficient of expansion match to GaN than the more common sapphire substrate. ATMI is uniquely suited to carry out this research as our MOVPE growth has reported one of the lowest background carrier concentrations (1016 cm-3) of any group growing nitride materials which is crucial to the fabrication of a low doped layer to act as the intrinsic region. The Phase II of this program will involve optimizing the p-i-n structure for increased responsivity and response time, shifting the wavelength cutoff to shorter wavelengths by using AlGaN, and finding a commercial partner to package the detectors for high-volume sale of UV detectors. GaN p-i-n photodiodes are an ideal choice for the solar-blind measurement of UV radiation for space-borne applications since these solid-state detectors are compact, light, and have low power consumption. Commercial applications include environmental monitoring, automobile engine combustion sensing, remote sensing of earth resources, solar UV monitoring, burner monitoring in gas turbines, and general purpose flame detection.