Reach Through APD (RTAPD)

optoex18.in : Reach Through APD (RTAPD)

Requires: Blaze/Luminous
Minimum Versions: Atlas 5.28.1.R

This example demonstrates:

  • An Avalanche PhotoDiode where Absorption and multiplication reions are separated. It also demonstrates the use of the Geiger mode to study its behavior as a sinlge photon counter at biases beyond breakdown.

The APD should maximize photon absorption. However the multiplication region should be thin in order to miminize secondary ionizations. These two conflicting requirements are acheived in Separate Absorption Multiplication (SAM) reach Through APD.

Advanced III-V heterostructures can be used to detect different wavelengths of light such as infra-red and ultraviolet. These heterostructures are often combined with silicon layers which are used for carrier multiplication. A typical example is shown here.

Since the device was mainly 1D we used the mesh auto feature of Atlas to create the structure. When using auto-meshing, you must only specify the mesh in the X direction using X.MESH statements. The mesh spacing in the Y direction is specified in the REGION statements. The REGION statement is used as well to specify the material types of individual "regions", their composition, doping, strain and certain other characteristics describing how the region is to be modeled.

The photogeneration rate is calculated using the beam statement. The beam was back illuminated for better gain in the linear region and a wavelength of 1um and a beam intensity of 0.1Watts/cm2 was used.

IV characteristics (dark as well under illumination) are simulated by ramping the anode voltage up to around -22V where the diode starts to break down and then beyond to -30V where the Geiger mode comes into play.

For the Geiger mode simulation, a probe statement was added so that the electron avalanche probabilities at the designated point versus bias could be seen on the log file.

The filename=optoex18_g option for the probe statement was used so that Geiger line integrals would be stored at bias points.

To load and run this example, select the Load button in DeckBuild > Examples. This will copy the input file and any support files to your current working directory. Select the Run button in DeckBuild to execute the example.