1. Optoelectronic Simulation of PhotoDetectors
Tarun Parmar
Microrelectronic Engineering
R.I.T.

2. Outline Introduction Comparison of Photodetectors Photon detection
Device Simulation
Optoelectronic Device Simulator
Results

3. Introduction
The poster presents simulation of recombination rate and quantum efficiency of an photodetector (photodiode) being fabricated at RIDL.
Simulated total integrated recombination rate significantly contributes to the reverse diode leakage current.
Quantum efficiency is defined as the ratio of the number of carriers detected at a given photodetector electrode divided by the number of incident photons on the detector.

4. Comparison of Photodetectors
Generic Operating Parameters of Si, Ge, and GaAs pin Photodiodes
Parameter
Symbol
Unit Si Ge
InGaAs
Wavelength Range λ nm
Responsivity R
A/W
Dark current ID nA
1-10
50-500
Rise time tr ns
0.5-1
Bandwidth B
GHz
0.5-3
1-2
Bias Voltage VB V 5
5-10
[Source: Optical Communications Essentials, Gerd Keiser, pp 113.]

5. Photon Detection pin photodiode operated in reverse bias
p+ – high acceptor concentration
intrinsic (lightly) doped material
n+ –high donor concentration
I-V characteristics of pin photodiode:
(1) with no light
(2) with light
Photons reach depletion region
produce e- – h+ pairs
electric field sweeps charges across junction
movement of charge results in a small current
mag. of this current @ incident light intensity

6. Device Simulation Device operation Operating parameters
e.g. electrostatic potential, carrier density, etc.
Equations involving parameters
e.g. Poisson’s, current continuity, transport, etc.
Mathematical modeling using models
e.g. SRH, Auger, Klassesen, Fermi, etc.
Simulation of the model
e.g. Silvaco, Spice, etc.

7. Optoelectronic Device Simulator
Luminous is an advanced simulator used to model absorption and photogeneration in semiconductor devices
Silvaco Athena simulation tool
Process simulation uses Athena
&
Electrical simulation uses Atlas, Luminous
Graphs are generated using Tonyplot

8. Tonyplot Results (1) Quantum Efficiency Recombination Rate
0.258 e-/sec/pixel

9. Tonyplot Results (2)
Electric field in 2D
Electric field in 3D