https://doi.org/10.15407/jopt.2018.53.188

Optoelectron. Semicond. Tech. 53, 188-198 (2018)

V.P. Maslov, A.V. Sukach, V.V. Tetyorkin, M.Yu. Kravetskii, N.V. Kachur, Ye.F. Venger, A.T. Voroschenko, I.G. Lutsishin, I. M. Matiyuk, A.V. Fedorenko

PECULIARITIES OF MANUFACTURE, ELECTRICAL AND PHOTOELECTRICAL PROPERTIES OF DIFFUSION Ge p-i-n-PHOTODIODES

The technological regimes for production of photosensitive Ge p-i-n-junctions by using simultaneous diffusion of acceptor impurities Zn and In with the two-temperature method in the n-Ge substrate possessing the specific resistivity close to 15 Ω cm in a closed system at the diffusion temperature of ~ 700 °C. The junction depth was of approximately 2 micrometers. To reduce the contact noise, p+-p- and n+-n structures were prepared. Thin polycrystalline ZnSe films of cubic modification were used for passivation and protection of the surface of the mezastructural p-i-n-transitions. The choice of ZnSe as a passive and protective coating was caused by the high specific resistance of polycrystalline films, good matching the lattice constants and coefficients of thermal expansion in contact materials. Technological regimes of depositing the ZnSe films have been presented, and the effect of vacuum-thermal processing the Ge junctions on minimization of surface currents in the heterojunctions and on stability of these passivating and protective coatings has been found. The basic mechanisms of charge carrier transport within the temperature range 227…316 K that corresponds to typical climatic conditions for junction operation, have been ascertained. It has been shown that in the studied temperature region, in forward- and reverse-biased junctions, the dark current is determined by diffusion and generation-recombination mechanisms with the dominant contribution of diffusion component. The basic parameters of the current-voltage characteristics (ideality coefficient, dark current at zero bias voltage, series resistance) have been determined, which allows to predict transport properties of the developed junctions at other temperatures. The influence of the i-region on the direct I-U characteristics has been revealed. Common behavior of the spectral dependences of current sensitivity under background radiation reduction by using a silicon optical filter embedded into the photodiode housing has been investigated, and threshold parameters of photodiodes have been also determined.

Keywords: Ge p-i-n-photodiodes, diffusion, passivation, transport properties, background radiation.