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

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

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.

Comparison of Photodetectors Generic Operating Parameters of Si, Ge, and GaAs pin Photodiodes Parameter Symbol Unit Si Ge InGaAs Wavelength Range λ nm 400-1100 800-1650 1100-1700 Responsivity R A/W 0.4-0.6 0.4-0.5 0.75-0.95 Dark current ID nA 1-10 50-500 0.5-0.2 Rise time tr ns 0.5-1 0.1-0.5 0.05-0.5 Bandwidth B GHz 0.3-0.7 0.5-3 1-2 Bias Voltage VB V 5 5-10 [Source: Optical Communications Essentials, Gerd Keiser, pp 113.]

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

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.

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

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

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