Improvement of dark current using InP/InGaAsP transition layer in large-area InGaAs MSM photodetectors |
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| Authors: | Junghwan Kim Johnson W.B. Kanakaraju S. Calhoun L.C. Lee C.H. |
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| Affiliation: | Dept. of Electr. & Comput. Eng., Univ. of Maryland, College Park, MD, USA; |
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| Abstract: | A large-area InGaAs metal-semiconductor-metal (MSM) photodetector with 1/spl times/1 mm/sup 2/ photoactive area for free-space optical communication applications has been designed, fabricated, and characterized. Interdigitated electrodes of 2-/spl mu/m widths and 15-/spl mu/m spacings are designed to maximize the responsivity, and enable MSM photodetectors to reach a maximum responsivity at 1.53-/spl mu/m wavelength. By employing a two-step InP/InGaAsP transition layer, the dark current density of 45 fA//spl mu/m/sup 2/ was achieved at 10-V bias and at room temperature. Dark current-bias voltage curves were measured as a function of temperature from 40 to 270 K to estimate the activation energy. A 3-dB bandwidth of 210 MHz was obtained at a 10-V bias, and the measured result was compared with the designed bandwidth. |
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