Design And Fabrication Of ALGAN-based Metal-Semiconductor-Metal Solar-belind Photodetectors

At present, AlGaN-based ultraviolet photodetectors (PDs) have received much attention for their importance in the range of ultraviolet wavelength. Because of the immunity from interference of visible light, solar-blind PDs is used for a wide range of military and commercial applications, such as the missile guidance and warning, ultraviolet communication and biochemistry analysis , biology and medicine analysis, etc.As the third generation semiconductor material of a direct band gap, GaN band gap is 3.4eV at the room temperature. With the variation of Al composition, band gap of ternary alloy AlGaN can be change from 3.4eV to 6.2eV continuously. This range which is absorbed by ozone layer of the Earth covers the main window of 200nm ~ 280nm. Because of intrinsic advantages of MSM structure, such as planar structure, simple preparation, without making a p-n junction, avoiding same issues such as doping and ohmic contact, easy to obtain high quantum efficiency, high responsiveness, ease of monolithic optoelectronic integration, etc, MSM structure become widely accepted.We have designed, fabricated, and characterized of AlGaN-based MSM ultraviolet PDs. The responsivity curves show that the cut-off wavelength of 276nm, indicating the PDs have a good solar-blind characteristic. The ultraviolet / visible rejection is about 3 orders of magnitude at 4V bias. The dark current was about 1nA at 1.5V bias and about 1μA at 5.3V bias. We analyzed the test results when the test was completed. Our work will not only provides some guides and references for the fabrication AlGaN-based MSM ultraviolet PDs with good performence, but also provides significant guiding in research of monolithic integration on UV focal plane array of AlGaN-based MSM structure.