Abstract:
The results of experimental studies of the effect of rapid thermal annealing on low-barrier diode structures used in the fabrication of microwave detectors for imaging arrays are indicative of an increase in the effective barrier height. Assuming that this effect is related to the diffusion spreading of the silicon $\delta$-doped layer, which determines charge transport in the modified diode, a theoretical model is developed and the diffusion coefficient for silicon in the near-surface region of gallium arsenide ($D\approx$ 2 $\times$ 10$^{-14}$ cm$^2$/s at 600$^\circ$C) is estimated. A comparison with published data makes it possible to assume that diffusion in the near-surface layers is greatly facilitated compared to that in the bulk. It is suggested that the cause of acceleration of the diffusion can be a high electric field formed by the charged plane of the detector and it can also be related to an increased density of defects near the surface. The practical result consists in the emerging possibility of increasing (within a certain range) the effective barrier height in the grown structures, which will make it possible to adapt the parameters of low-barrier diodes to the optimal value in order to obtain sensitive detectors.
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