Abstract
We report the fabrication of novel self-biased high resolution radiation detectors achieved in n-type 4H-SiC metal-oxide-semiconductor (MOS) devices. Vertical MOS structure has been realized by pulsed laser deposition of 40 nm Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> layer on 20 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> n-type 4H-SiC epilayer followed by sputter coating a nickel gate, which revealed a record-high hole diffusion length. The MOS device exhibited a remarkable radiation detection response to 5486 keV alpha particles with a charge collection efficiency of 82% and an energy resolution of 72 keV full width at half maximum (FWHM) at zero applied bias. The hole diffusion length has been calculated to be 56 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> using a drift-diffusion model. Such long hole diffusion length and a flat-band potential of 2.1 V, enabled to attain high efficiency and resolution in the self-biased mode. Band energy calculations indicated that the presence of Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> layer may have neutralized the hole traps usually present in a metal-4H-SiC interface thereby substantially improving the hole transport. Such high performing self-biased radiation detectors fabricated on 4H-SiC are intended for applications in harsh environment space missions, wherein carrying detector power supplies as a payload becomes a critical logistic issue. The present study opens the high potential of other wide bandgap semiconductors as self-biased MOS devices as well.
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