Spectral photosensitivity of diffused Ge-p–i–n photodiods

Laser rangefinders are widely used to measure distances for various civil and military purposes, as well as in rocket and space technology. The optical channel of such rangefinders uses high-speed p–i–n, or avalanche, photodiodes based on Si, Ge or InGaAs depending on the operating wavelength of the rangefinder in question. The paper describes a manufacturing process for high-speed Ge-p–i–n photodiodes for laser rangefinders using the diffusion method. The passivation layer is made of ZnSe, which is a new solution for this type of photodiodes. The existing theoretical models are used to study the spectral ampere-watt sensitivity of the diodes at various values of the active region parameters, and the simulation results reliability is evaluated by the respective measurements. It is shown that the obtained theoretical dependence well agrees with the measurement data. Moreover, the authors for the first time study the spectral photosensitivity of the Ge-p–i–n photodiode with a coated silicon filter covering the range λ = 1.4—1.6 μm. The spectral sensitivity range for the diodes is determined to be λ = 1.1—1.7 μm. The maximum photosensitivity of 0.42 A/W is achieved at a wavelength of λ = 1.54 μm. The authors argue that Ge-p–i–n photodiodes with a silicon filter are resistant to the “blinding” laser radiation with λ = 1.064 μm. The calculated data on the spectral photosensitivity of the photodiode with a filter also well agree with the experiment. Thus, the chosen simulation technique allows taking into account most design and technological characteristics of the photodiodes during theoretical simulation, which makes it possible to accurately predict and optimize their parameters for a specific practical task and improve the manufacturing process of the photodiodes.