Sensitivity analysis of integrated InGaAs MSM-PD´s and HEMT optoelectronic receiver array

A sensitivity analysis is given of a long wavelength optoelectronic receiver array consisting of InAlAs/InGaAs interdigitated Metal Semiconductor Metal photodetectors (MSM-PD´s) and a HEMT preamplifier. It is shown that the capacitance varies with the finger width and spacing for a MSM-PD with same active area. Analytical expressions are derived for calculating the sensitivity of the receiver array by means of the equivalent circuit models of the MSM-PD´s array and the HEMT. Major noise sources in the receiver array, such as shot noise in the photodetectors, thermal noise in the resistors, gate and drain noises as well as their correlation term in the HEMT, are considered. The influences of geometric parameters of the MSM-PD´s and HEMT on the sensitivity of the receiver array are investigated. The optimum gate width of the HEMT is determined for a given MSM-PD array to obtain a high receiver sensitivity. It is also demonstrated that the optical signal related shot noise from the MSM-PD´s makes a substantial contribution to the total noise of the receiver array