چكيده به لاتين
In recent decades, InP/InGaAs avalanche photodiodes have attracted much attention in laser warning and long distance optical communication systems due to their high bit rate and gain-bandwidth. Laser warning systems are used to detect optical signals in the near-infrared wavelength range (NIR) and protect operating systems such as factories, ships, and more. Laser warning include several subsystems, among which the detection subsystem plays an important role. The physical limitations imposed by the sun's exposure to laser warning and the attenuation of the atmosphere have made it difficult to detect low-power (1-10μW) laser threats. Therefore, avalanche detectors were used for their high sensitivity.
In this thesis, to improve the noise characteristics in laser detection systems, separate absorption, grading, charge, and multiplication InP/InGaAs avalanche photodiode (SAGCM APD) with double guard rings and three thin layers of InGaAsP has been simulated. In addition, the multiplication width of SAGCM APD has been optimized which enhances the noise characteristics.
The excess noise factor in the constant mean gain of 10 has been reduced 10.3% in comparison with recent SAGCM APDs. The Photocurrent and dark current are acquired as 40 μA and 0.01 nA resulting in superior electrical properties among the other works. Thus, the efficiency and photo-responsivity of detection system are increased and noise characteristics are decreased. According to simulations, the breakdown, punch-through and bias voltages at mean gain of 10 are 39 V, 14 V and 37 V, respectively which lead to simplification of the biasing and reduction of the power consumption. The calculated results show that the reduction of dark current and the excess noise factor increase the SNR for about 5 orders of magnitude.
