Photoemission-based microelectronic devices

Abstract

The vast majority of modern microelectronic devices rely on carriers within semiconductors due to their integrability. Therefore, the performance of these devices is limited due to natural semiconductor properties such as band gap and electron velocity. Replacing the semiconductor channel in conventional microelectronic devices with a gas or vacuum channel may scale their speed, wavelength and power beyond what is available today. However, liberating electrons into gas/vacuum in a practical microelectronic device is quite challenging. It often requires heating, applying high voltages, or using lasers with short wavelengths or high powers. Here, we show that the interaction between an engineered resonant surface and a low-power infrared laser can cause enough photoemission via electron tunnelling to implement feasible microelectronic devices such as transistors, switches and modulators. The proposed photoemission-based devices benefit from the advantages of gas-plasma/vacuum electronic devices while preserving the integrability of semiconductor-based devices.

Figure 1. The designed photoemission-based device.

(a) Biased resonant inclusions of each port under illumination by a CW laser can emit electrons, (b) the free electrons can be manipulated electrically by applying voltage V_f on the flat port and V_s on the suspended port. The grounded (GND) terminal of each port is specified.

Figure 2. The designed resonant surface.

(a) Dimensions of the unit cell are a=100 nm, b=100 nm, c=150 nm, d=80 nm, e=70 nm, g=50 nm, r=240 nm, L=850 nm, W=880 nm, h=225 nm, (b) full wave (ANSYS HFSS) simulated electric field enhancement at the center of the gap between the inclusions, and (c) the electric field magnitude distribution at λ=785 nm (red colour represents the highest value). This figure only shows the laser-surface interaction, and there are not any bias voltages involved.

Figure 3. SEM pictures of the fabricated electron emission-based device.

(a) The resonant surface, (b) the entire device including the wire-bonding pads, (c) the airbridges on the two sides are for biasing mushroom rows with alternating polarities, to form the suspended port, (d) the parallel strips on the substrate, below the mushrooms, form the flat port.

Figure 4. Individual port responses.

(a) I–V curves of the suspended/flat port as the flat/suspended port is open-circuited (I=5 W cm⁻²), (b) experimental responsivity of the flat port (markers) and their first order interpolation (line). V_f and I_f are voltage and current of the flat port, respectively. (c) Frequency dependence of the suspended port's response. Markers show the measured points, and the line is their first order interpolation. V_s and I_s are voltage and current of the suspended port, respectively.

Figure 5. The mutual response between the two ports.

(a) I–V curves of the flat port as the suspended port is biased with different voltages, with (w/) and without (w/o) the laser illumination. laser intensity is I=5 W cm⁻², and subscripts f and s denote the flat and the suspended ports, respectively. (b) The induced current on the flat port as V_f is fixed at zero and V_s varies, (c) the small-signal transconductance (|g|) of the device (V_f=0), (d) the induced sinusoidal current on the flat port due to the applied sinusoidal voltage on the suspended port (V_f=0, I=40 W cm⁻²).