Some properties of reverse-biased silicon carbide p - n junction cold cathodes

The Kuga-Satake variety of a Kummer surface

“…When log I, was plotted against V, (the extraction field) for various values of Vj, as shown in figure 2, two of the cathodes gave an emission peak at V ' = 70 V superimposed on the usual characteristic (see Bellau and Widdowson 1972, figure 6) for the higher values of Vj. This effect is attributed to the emitted electrons which are returned by the crystal field to bombard the oxide film covering the n type S i c with an energy only a few volts less than the junction voltage.…”

“…This effect is attributed to the emitted electrons which are returned by the crystal field to bombard the oxide film covering the n type S i c with an energy only a few volts less than the junction voltage. (The electron optics of this phenomenon is described by Bellau and Widdowson (1972) and illustrated in figure 7 of this paper.) The secondary emission coefficient of this oxide surface apparently rose above unity at a bombardment energy of about 20 V, thus increasing the number of electrons leaving the S i c for values of above 24 V. This abnormally low value for the first crossover potential (the potential at which the secondary emission coefficient first reaches unity as the potential increases) arises from the high temperature of the oxide surface.…”

“…Electron emission from silicon oxide into Now at The M-O Valve CO Ltd. Brook Green Works, Hammersmith, London W6 'PF vacuum has been reported by Verderber and Simmons (1967) and by Elinson et a1 (1959). Secondly, it was shown by Bellau and Widdowson (1972) that the junction current in an activated emitter could be regarded as comprising two separable components, (i) the bulk current, a function of the junction voltage and which does not change during the development of emission, and (ii) a surface current ljs which increases as emission is developed and appears to be related to V, by a power law Ijs = kVy, It is difficult to devise a mechanism in which the conduction can be simultaneously controlled by laws of such widely different functional forms, but a simple explanation can be obtained by assuming that the bulk current is a constant property of the S i c p-n junctions, while the surface current across the p-n junction does not pass through S i c but through a heavily doped oxide film on the surface. It will be shown that this assumption affords a ready explanation of many other experimental observations and it appears to give a feasible mechanism for the emission from reverse-biased p-n junctions in S i c and Si.…”

“…The numerical values of electron affinity, bandgap and diffusion length for Sic and for Si seem to afford an explanation for the observed emission from p-n junctions in S i c and also for the very poor emission from Si except when the electron affinity is reduced by the adsorption of Cs or Ba. However, the relevance of these ideas began to be questioned when an analysis was made of the results of some recent investigations into electron emission from Sic reported by Bellau et a1 (1971) and by Bellau and Widdowson (1972).…”

“…It has been found by Bellau and Widdowson (1972) that, in order to develop emission from a S i c cathode the relevant regions of the surface must be heated to 600-700°C. In addition, Allam and Pitt (1967) report that at a temperature of about 600°C amorphous thin films of SiO, change to a pseudocrystalline structure comprising SiO, tetrahedra with oxygen links (see also Sugano et al 1968).…”