Modeling and characteristics of MWIR HgCdTe APD at different post-annealing processes

• Mid-wavelength infrared (MWIR) HgCdTe electron-initiated avalanche photodiodes (e-APDs) have presented excellent performances to resolve and count photons with linear mode. However, there is a lack of research on the fundamental mechanism of HgCdTe APD device fabrication processes influence over its performance. In this paper, we detailed the modeling and characteristics of diodes under different fabrication processes. • The specific significance of this work described as follows: • 1. Proper fabrication processes can keep the peak electric field away from the implantation damage region, effectively increase the Shockley–Read–Hall (SRH) lifetime, reduce the multiplication region concentration and finally increase the operating voltage. • 2. The dark current for HgCdTe APD is dominated by I concentration when I region width reaches a certain value, the lower the I concentration is, the smaller the dark current is. • 3. Tuning Cd composition (from 0.298 to 0.332) could be a trade-off way for GNDCD suppression, which is supposed to approach ∼ 10 -10 A/cm 2 @-10V. • All in all, our work provides theoretical and experimental guidance for improving performance of HgCdTe APD. Mid-wavelength infrared (MWIR) HgCdTe electron-initiated avalanche photodiodes (e-APDs) have presented excellent performances to resolve and count photons with linear mode. Aiming at low flux, the ROIC noise can be extremely reduced by certain gain, and very low excess noise makes opportunity for noise equivalent photon (NEPh) to be 1. Therefore, the main issue for SNR of HgCdTe APD is gain normalized dark current density (GNDCD) at high reverse bias. In this work, the architecture of multiplication region is modeled and studied. The depth and width of multiplication region are controlled by regulating the p-type doping concentration, ion implantation and post thermal annealing conditions as well. Proper processes can keep the peak electric field away from the implantation damage region, effectively increase the Shockley–Read–Hall (SRH) lifetime, reduce the multiplication region concentration and finally increase the operating voltage. Considered with dark current and gain, depletion region ( I region) width is optimized and characterized to be 3 ∼ 3.6 μm when I region concentration is ∼ 1×10 15 cm -3 in our case. The GNDCD of MW APD (cut off wavelength ∼ 5.16 μm @80k) is less than 10 -6 A/cm 2 @≤-10V, with avalanche gain of ∼ 1570@-9.8V. The excess noise factor ( F ) is measured to be 1-1.4 by noise power spectral density (PSD). The NEPh value is less than 5 photons with gain up to ∼ 280 for MW 128×128 HgCdTe APD array. Simulation results anticipate that GNDCD can be further reduced by decreasing the doping concentration of I region to below 5×10 14 cm -3 . Furthermore, increasing the p-type doping concentration and band gap will significantly reduce GNDCD below to ∼ 10 -10 A/cm 2 @-10V for 4.22 μm Hg 1- x Cd x Te ( x = 0.332) APD.