Schottky Photodiode

- a summary of the Schottky photodiode detailing the basics of its operation, applications and other salient features.

Photodiode tutorial includes:

See also: Diode types     Phototransistor

The Schottky photodiode is based around the Schottky barrier diode and it may also be called the metal-semiconductor diode as a result of its structure.

The Schottky photodiode provides additional capabilities over other forms of photodiode in terms of speed and long wavelength detection capability. As a result the Schottky photodiode has a unique niche in amongst the other forms of photodiode that are available.

Schottky photodiode basics

As the name indicates, the Schottky photodiode uses the Schottky diode (or Schottky barrier diode as it is sometimes called) as its basis of the photodetector.

The Schottky photodiode is unique as a photodetector as it is able to operate in two photo-detection modes:

• Electron pair generation:   This occurs from band to band or energy gap excitation in the semiconductor.
• Emission of carriers:   The emission of carriers occurs from the metal to the semiconductor over the Schottky barrier. This often referred to as internal photoemission.

The metal-semiconductor junction provides a similar action to that of the intrinsic layer of the PIN photodiode. Accordingly is provides a larger areas for capture of the photon energy.

Schottky photodiode applications

The Schottky photodiode is particularly compatible with mature silicon and silicide technology. As a result these photodiodes have been widely used in CCD - charge coupled device - as the image sensing photodetector.

The Schottky photodiode can be integrated into a single chip along with CCD transfer gate - these are also compatible with silicon technology. The CCD itself forms a shift register to allow the data from the array of Schottky photodiode detectors to transferred out of the overall chip in a managed way - providing method of extracting the huge data files from the large array of photodetectors with a sensible number of leads on the integrated circuit.

As a result of these advantages the Schottky photodiode detector has been the most widely used technology for focal plane arrays.

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