EUV detectors based on AlGaN-on-Si Schottky photodiodes

Abstract

Photodetectors designed for the Extreme Ultraviolet (EUV) range with the Aluminum Gallium Nitride (AlGaN) active layer are reported. AlGaN layers were grown by Molecular Beam Epitaxy (MBE) on Si(111) wafers. Different device structures were designed and fabricated, including single pixel detectors and 2D detector arrays. Sensitivity in different configurations was demonstrated, including front-and backside illumination. The latter was possible after integration of the detector chips with dedicated Si-based readouts using high-density In bump arrays and flip-chip bonding. In order to avoid radiation absorption in silicon, the substrate was removed, leaving a submicron-thin membrane of AlGaN active layer suspended on top of an array of In bumps. Optoelectrical characterization was performed using different UV light sources, also in the synchrotron beamlines providing radiation down to the EUV range. The measured cut-off wavelength of the active layer used was 280 nm, with a rejection ratio of the visible radiation above 3 orders of magnitude. Spectral responsivity and quantum efficiency values were extracted from the measurements to enable comparison with the state-of-the-art UV photodetectors.

Pulsed growth techniques in plasma-assisted molecular beam epitaxy of Al Ga1−N layers with medium Al content (x=0.4–0.6)

“…Al x Ga 1 À x N layers with high Al content (x4 0.4) is an attractive material for development of ultraviolet (UV) light emitting and laser diodes [1][2][3], photodiodes and photocathodes [4,5] highly demanded for numerous applications. Low temperature (o 800 1C), high vacuum ( $10 À 5 Torr), and hydrogen-free environment of plasma-assisted molecular-beam epitaxy (PA MBE) gives rich possibilities in realization of quantum heterostructures, their strain engineering, and p-type doping.…”