Silicon four element p-i-n photodiode with improved characteristics

Abstract

This article presents the results of the development of silicon coordinate p-i-n photodiodes (PD) with improved parameters. The technological possibilities of reducing the gaps between the responsive areas of multi-element PDs were studied. PDs with reduced gaps were modeled, samples were made according to the models, the parameters of the obtained PDs and the influence of various technological factors on their values were investigated. During research, it was established that the factor that limits the possibility of reducing the gaps is the insulation resistance between the responsive elements. The decrease in the insulation resistance between the PD elements was a consequence of the formation of inversion leakage channels at the Si-SiO2 interface, which is characteristic of high-resistance p-type silicon, the conductivity of which increased with a decrease in the width of the gaps. To increase the resistance of the gaps between the platforms and reduce the influence of inversion layers, it was decided to form regions of the restriction of the leakage channels between the REs – highly doped regions isotypic with the substrate material (p+-type). They will prevent the movement of current carriers that are generated in the inversion layers on the surface of the substrate. Four-element p-i-n photodiodes with 31 μm gaps between the sites were made. The proposed PD is not significantly inferior in parameters to analogues, but it is the sample with the smallest gaps between RE among photodiodes of the same type and size in the world market. The improvement of the insulation resistance between the REs made it possible to reduce the level of dark current of the PD by twice compared to serial products, with a slight decrease in responsivity due to the introduction of additional thermal operations into the technological route. In particular, the dark current density of the RE of experimental PDs was 40-80 nA/cm2, compared to 80-250 nA/cm2 for commercial samples. Impulse current monochromatic sensitivity at a wavelength of 1064 nm for experimental samples was 0.41-0.44 A/W, and for commercial ones - 0.45-0.48 A/W.