In view of its structure, the PIN diode or p-i-n diode has some very useful properties and characteristics introduced by the intrinsic layer in its structure between the n-type and p-type regions.
As result of these characteristics, the PIN diode is used in a number of areas where its properties and characteristics make it uniquely applicable for a number of applications.
While the PIN diode characteristics mean that it is not suitable for many standard rectifier applications, they provide some properties that can be used in a number of specific areas.
PIN diode characteristics
There are a number of PIN diode characteristics that set this diode apart from other forms of diode. These key PIN diode characteristics include the following:
- Low capacitance: Again the intrinsic layer increases the depletion region width. As the capacitance of a capacitor reduces with increasing separation, this means that a PIN diode will have a lower capacitance as the depletion region will be wider than a conventional diode. This PIN diode characteristic can have significant advantages in a number of RF applications - for example when a PIN diode is used as an RF switch.
- High breakdown voltage: The wide depletion layer provided by the intrinsic layer ensures that PIN diodes have a high reverse breakdown characteristic.
- Sensitive photodetection: The sensitive area of a photodiode is the depletion region. Light striking the crystal lattice can release holes and electrons which are drawn away out of the depletion region by the reverse bias on the diode. By having a larger depletion region - as in the case of a PIN diode - the volume for light reception is increased. This makes PIN diodes ideal for use as photodetectors.
- Carrier storage: Carrier storage gives a most useful PIN diode characteristic. For small signals at high frequencies the stored carriers within the intrinsic layer are not completely swept by the RF signal or recombination. At these frequencies there is no rectification or distortion and the PIN diode characteristic is that of a linear resistor which introduces no distortion or rectification. The PIN diode resistance is governed by the DC bias applied. In this way it is possible to use the device as an effective RF switch or variable resistor for an attenuator producing far less distortion than ordinary PN junction diodes.