Figure 3: Microwave active GaAs electronic devices on CNF paper.

(a) Photograph of an array of HBTs on a CNF substrate put on a tree leaf. (b) Magnified photograph of the array. (c) Gummel plot and β plot showing the maximum DC gain of the HBT. The maximum β is 14.49. The inset optical image shows one of the HBTs in the array that was measured and characterized. (d) I_C versus V_CE plot of the HBT plotted at 0.5 mA steps of I_B. (e) Current gain (H₂₁) and power gain (G_MAX) as a function of frequency, with a collector voltage bias of 2 V and a base current bias of 2 mA. (f) Current versus voltage plot of the Schottky diode on a CNF substrate. The red curve shows the logarithmic scale and the blue curve shows the linear scale. The inset optical image shows the diode transferred onto a CNF substrate with G–S–G interconnects. (g) Measured S₁₁ (red) and S₂₁ (blue) plotted against frequency under a forward current bias of 10 mA. (h) Measured S₁₁ (red) and S₂₁ (blue) plotted against frequency under a reverse voltage bias of −0.5 V.