Gallium nitride on silicon UV sensor offers high responsivity
Researchers at Brown University (Providence, RI) have merged the ultraviolet (UV) capabilities of grou¥III nitrides with silicon microelectronics. They have demonstrated a UV photo detector made from magnesium-doped gallium nitride (GaN:Mg) on silicon with responsivity of 12 A/W at 4-V bias. This performance was sustained for UV intensities of 1 W/m2 and below. Photocurrent is nearly linear versus intensity for u¥to 10 W/m2 with a maximum responsivity of 30 A/W at 14-V bias. Responsivity is linear with applied voltage u¥to 8 V, then slows toward saturation. The investigators hypothesize that such performance is caused by positive holes being captured and held immobile at magnesium-related acceptor sites or trap/recombination centers, resulting in a greatly prolonged electron free-carrier lifetime.
Development of GaN sensors may lead to unique UV/visible imaging arrays. Such photo detector applications include sensing rocket and jet exhaust plumes in the atmosphere, solar-UV radiation reflected off spacecraft, and flames in the presence of a hot background, as in furnaces.