Reduction of 1/f noise in multiplexed linear In/sub 0.53/Ga/sub 0.47/As detector arrays via epitaxial doping

A significant (2-5*) reduction in 1/f noise was observed in In/sub 0.53/Ga/sub 0.47/As photodetector arrays read out by a PMOS multiplexer, when the epitaxial InP cap layer doping was changed from undoped to sulfur-doped n type of about 3*10/sup 16/ cm/sup -3/. A further decrease was observed when the InP buffer layer was also changed from undoped to sulfur-doped n type of about 5*10/sup 17/ cm/sup -3/. Data was presented for the variation of 1/f noise, within a temperature range of 18 degrees C to -40 degrees C. Surface states at the InP cap/SiN interface appears to be the primary source of 1/f noise, with the bulk states at the n/sup -/In/sub 0.53/Ga/sub 0.47/As buffer hetero-interface as a secondary source. Increased n-type doping in the high-bandgap InP cap and buffer layers may reduce electron trapping, and thus 1/f noise. The measured noise spectrum of InGaAs photodetectors varies as f/sup y/ with y being approximately -0.45 for device structures with doped and undoped InP can layers. For a doped InP buffer layer, this value of y is -0.3.<
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