A position sensitive detector based on an ITO - Si structure

Abstract

One-and two-dimensional position sensitive detectors based on an ITO-pSi structure have been fabricated and studied. The experimentally measured linear dependence between the photovoltage response and the light spot position is explained by a model in which the electric field in silicon in the lateral direction (E Si ) is assumed to be constant. It has been shown that E Si is inversely proportional to the electron diffusion length. Using the experimental data the electron diffusion length is estimated to be about 1 cm.

Modelling the operation of an a-Si:H based position sensitive detector

“…Therefore the photoelectrons can recombine only if they pass through the a-Si:H layer into the Pd against the internal field. Effective electron diffusion length of the same order has been found for a PSD based on another structure, ITO/crystalline silicon [10]. Also in [10] it has been established that L eff strongly depends on the recombination velocity at the lateral edges of the structure.…”

“…It can be seen that in these coordinates the dependence is approximately a straight line with a slope 1.52 cm −1 . Using formula (10) an estimation of the electron diffusion length gives L eff ≈ 0.65 cm. This large value may be explained in the following way: since ITO is degenerately doped it may be expected that, similar to metals, the electric field cannot penetrate deeply into it.…”

“…Using equation (10) the PSD output voltage ψ(x) = ψ 1 (x) − ψ 2 (x), where ψ 1 (x) and ψ 2 (x) are the photovoltages on the first and the second position contacts, can be expressed as:…”

“…In addition, one dimensional models are also restricted in the description of PSD operation because they do not take into account the recombination process at the edge of the structure parallel to the x-axis. This recombination process has substantial influence on the output voltage characteristics [10].…”

Electron-beam fabricated titanium and indium tin oxide position-sensitive detectors

“…There has been some work on crystalline PSDs (Wallmark 1957, Morikawa and Kawamura 1992, Geist 1994, Georgiev et al 1997, but most of the e ort has concentrated on complex multilayer amorphous silicon p±i±n structures (Takeda 1991, Fortunato et al 1996, Martins and Fortunato 1999. The Schottky barrier devices fabricated in our work have been shown to have some excellent sensitivities, linearities and minimum spot detection parameters.…”