Photoresponse of gated p-silicon field emitter array and correlation with theoretical models

Abstract

Improved fabrication and conditioning techniques for gated p-Si field emitter arrays (FEAs) (1×1mm2 in size with 50×50 emitters) greatly reduces the bulk damage and surface states. Consequently, only 0.9μA of the anode dark field-emission current was measured for 50V applied gate potential with a very low gate leakage current. At these low gate leakage currents, the transition between the tunneling-limited field-emission regime and the supply-limited saturation regime is clearly revealed in current-voltage plots. This transition is accompanied by a reduction in the anode current fluctuation. The standard deviation of the noise current drops from a few percent in the tunneling-limited regime to <1% in the supply limited regime at 50V. A photocurrent of 0.41mA was obtained for photoexcitation at 840nm wavelength. This corresponded to 40dB contrast ratio between the photocurrent and the dark current at room temperature. Additionally, our findings showed that surface states were fully depleted at low applied fields, the concentration of bulk defects was low and the area contributing to the dark current was confined to the emitter regions. In contrast, previously reported ungated Si field emitters had high concentrations of surface states and bulk defects. Furthermore, the contributing area to the dark current corresponded to the whole area of the device as opposed to only the emitter areas for a gated FEA. Photofield emission and dark current measurements from our gated p-Si FEA correlate well to theoretical models without requiring cooling to liquid-nitrogen temperatures.

Characterization of an InGaN-based photo-emissive device

“…In Figure 5, once the maximum available optically generated electrons are extracted, the emission current saturates because there are no other electron sources within the photocathode film. What differentiates these results from other photo-field emission [13,16] results is that there is no indication of tunneling through a barrier potential at the surface. This observation is supported by the observed low field behavior.…”

Strong deviations from Fowler-Nordheim behavior for field emission from individual SiC nanowires due to restricted bulk carrier generation

“…This conclusion is supported by the field dependence of E A as expected for a Poole-Frenkel mechanism 38 and by the increasing current as a function of voltage in regime II instead of nearly perfect saturation. Varying slopes in regime II have also been observed by others 19,20 and are attributed to the weight of additional transport mechanisms, especially the Poole-Frenkel effect. The difference in E A between the lowtemperature and high-temperature regimes explains why even in an insufficiently cleaned sample as in Fig.…”

“…1͒ as the current follows or deviates with respect to standard FN theory. The regimes are predicted by theory 16 and have been verified in experiment [17][18][19][20] for properly prepared macroscopic FE tips. In particular for the p-type case ͑see Fig.…”

“…The two mechanisms are experimentally distinguishable because the activation energy will be E gap / 2 for n i 2 and E gap for n i -type carrier generation, respectively. An even further refined model, 20 including the effect of trap charges, gives a more complicated activation energy that depends on E gap / 4 for a specific geometry of the emitter. For an n-type semiconductor, the saturation current is due to thermally generated electrons from the dopant to the conduction band.…”

Photoemission-based microelectronic devices

“…However, photoemission can be greatly enhanced by the excitation of collective electron modes of the metal, called surface plasmon polaritons (SPPs), and laser intensities on the order of 1 GW cm −2 in the mid-IR have been shown to be enough for photoemission18. In photomultiplier tubes19 and field emitter arrays72021, a static bias is typically used to decrease the potential barrier of the material, enabling it to emit electrons with light. This combination can provide great sensitivity (single photon in case of a photomultiplier tube) or high electron emission (bright electron beam in case of field emitter arrays).…”