4H-SiC P + N UV Photodiodes : A Comparison between Beam and Plasma Doping Processes
Abstract: This paper presents a study of 4H-SiC UV photodetectors based on p+n thin junctions. Two kinds of p+ layers have been implemented, aiming at studying the influence of the junction elaborated by the ion implantation process (and the subsequent annealing) on the device characteristics. Aluminum and Boron dopants have been introduced by beam line and by plasma ion implantation, respectively. Dark currents are lower with Al-implanted diodes (2 pA/cm2 @ - 5 V). Accordingly to simulation results concerning the influence of the junction thickness and doping, plasma B-implanted diodes give rise to the best sensitivity values (1.5x10-1 A/W @ 330 nm).
Summary (1 min read)
- During the past years there has been considerable interest in systems able to record very low light levels in the ultraviolet range in severe conditions of use.
- It is then possible to use SiC for fabrication of devices capable to operate under extreme conditions.
- Photodetectors based on SiC allow to obtain good wavelength selectivity in the UV range, without any optical filters.
- The role of the p + emitter layer properties has been particularly studied in this paper.
- This concentration discrepancy takes into account the difference of ionisation energies between Al and B dopants, and should give rise to similar values of the final hole concentrations in p + layers.
- The back contact on the substrate was annealed at 900°C and the contact on implanted layer was annealed at 800°C.
- The optical simulations of photodetectors under the UV light have been realised by FDTD method (Finite Difference Time Domain), using the commercial software Sentaurus edited by Synopsys society .
- A former study proved that, at a given energy, the plasma-process leads to a better surface morphology, a lower defect concentration and a thinner junction than a standard beam implantation process.
- The evolution of dark currents with reverse bias of the realised devices is shown in Fig.4.
- Fig.5 displays the evolution of the “signal-to-noise” ratio with reverse bias.
- For a given annealing temperature, B-implanted diodes give rise to a higher signal than Al-implanted diodes.
- R e s p o n s iv it y ( A /W ) Wavelength (nm) Fig.6 Spectral responsivities of Alimplanted photodetector (the power source light is shown in the inset) Fig.7 Spectral responsivities of Al- and Bimplanted photodetectors.
- Boron plasma-implanted devices give rise to the best spectral responsivities.
- The behaviour of the diodes after irradiations is currently under study.
Did you find this useful? Give us your feedback
Cites background from "4H-SiC P + N UV Photodiodes : A Com..."
...All the above issues can be partially overcome by fabricating small area devices , ....
Related Papers (5)
Frequently Asked Questions (1)
Q1. What have the authors contributed in "4h-sic p+n uv photodiodes : a comparison between beam and plasma doping processes" ?
This paper presents a study of 4H-SiC UV photodetectors based on p + n thin junctions.