Gallium nitride on silicon UV sensor offers high responsivity

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.