Enhanced Hole Transport in Ni/Y₂O₃/n-4H-SiC MOS for Self-Biased Radiation Detection

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
₂
O
₃
layer on 20
$\mu \text{m}$
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
$\mu \text{m}$
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
₂
O
₃
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.