4 A/cm², 7kV normally-off diamond-emitter vacuum switch

Abstract

We have been proposed ultra-high voltage vacuum switches using diamond pin diode-type electron emitters with a negative electron affinity. Based on the previous 10 kV demonstration, our recent progress on high current operations above 1 A/cm 2 in the vacuum switch is presented. High voltage of 7kV normally-off operation was confirmed, and then we evaluated the capability of this device based on our model.

Ultrawide‐Bandgap Semiconductors: Research Opportunities and Challenges

“…Diamond also has the highest known thermal conductivity of any material, of particular importance because in so many power electronics and optoelectronics applications device operation is limited by heat removal. Some additional unique properties include: excellent electron emissivity on hydrogen terminated surfaces, [49,50] surfacetransfer doping enabled by these hydrogenterminated surfaces, [51] room-temperature UV exciton emission, and optical defect centers due to the nitrogen-vacancy (N-V) and silicon-vacancy (Si-V) complexes. These defect centers have been proposed, as discussed in Section 4.5, as a physical qubit platform for emergent quantum information systems.…”

“…Indeed, diamond surfaces have demonstrated thermionic energy conversion, while pin diodes with H-terminated surfaces have shown efficient electron emission at room temperature and have been used in high voltage (≈10 kV) vacuum switches. [50] But the low electron affinity of diamond also enables surface doping on intrinsic diamond surfaces (similar to polarization doping in AlGaN/ GaN). Early studies established that air adsorbates could lead to a two-dimensional hole gas (2DHG) with a sheet charge density in the 10 14 cm −2 range.…”

“…Reports have shown emission efficiencies that approach 2.5% of the diode current, similar to the efficiency of thermionic cathodes. [49,50] There is also interest in other UWBG materials for electron emission. A negative electron affinity has been found for hydrogen-terminated c-BN, [259] and ammonia-exposed surfaces of AlN have shown an electron affinity of less than 1 eV.…”

Diamond power devices: state of the art, modelling, figures of merit and future perspective

“…Hydrogen-terminated diamond interfaces are well known to exhibit a unique property renowned in the literature as NEA, already discussed in section 2.3.2. This feature is very attractive for the realization of electron emitters as, from a theoretical point of view, electrons excited from the valence band or injected from contacts into the conduction band could be efficiently emitted in vacuum from the surface without any increase of the device temperature [166][167][168][169][170].…”