Effect of dimensional parameters on the current of MSM photodetector

In this work, we present the influence of dimensional parameters on dark current and photocurrent of the metal–semiconductor–metal photodetector (MSM). MSM photodetectors of different sizes have been fabricated on GaAs (NID). The active area of MSM samples varies between 1×1 μm2 and 10×10 μm2 with equal electrodes spacing and finger widths (l=D) varying between 0.2 and 1 μm. The I(V) characterization in inverse and direct polarization in darkness shows good symmetry of curves, which shows the good performance of components and successful fulfillment of the Schottky contacts. The application of laser fiber of incident light power of 16 mW at wavelength of 850 nm for the illumination of the MSM photodetectors showed the evolution of the photocurrent ranging from 0.75 to 1.81 mA, respectively, for 1 to 0.2 μm electrodes spacing at 3 V and active area S=3×3 μm2. We showed also that variation ranging from 0.45 to 2.5 mA, respectively, for S=1×1 μm2 to S=10×10 μm2 at 3 V and 0.3 μm electrodes spacing. The resistance of MSM photodetectors obtained evolved proportionally to the electrodes spacing (0.87 kΩ for D=0.2 μm and 2.27 kΩ for D=1 μm with S=3×3 μm2) and inversely proportional to the surface area (2.02 kΩ for S=1×1 μm2, and 0.56 kΩ for S=10×10 μm2 with 0.3 μm inter electrodes spacing).

► Good technological realization of MSM photodetectors on GaAs (NID).
► Typical DC characteristics of MSM photodiodes were obtained.
► Breakdown voltage vs. electrodes spacing are presented.
► Evolution of the photocurrent versus bias voltage is presented.
► Variation of MSM resistance vs. surface area for different electrode spacing.