RSoft Feature Close-Up: Co-Simulation Using Sentaurus TCAD and RSoft Products

Efficient, Robust Optoelectronic Analysis Using Native File Formats

The RSoft Photonic Component Design Suite is integrated with Synopsys Sentaurus TCAD products to provide streamlined, multi-disciplinary simulations of complex optoelectronic devices. It is a bi-directional interface that uses native file formats for efficient, robust analysis – with no messy file format conversions.

Sentaurus TCAD geometry can be imported into RSoft photonic design tools such as FullWAVE for finite-difference time-domain (FDTD) analysis, BeamPROP for rapid analysis of silicon photonics devices and DiffractMOD for diffractive optical structure analysis.

In addition, RSoft photonic design tools are integrated into the Sentaurus Workbench for easy inclusion in a Sentaurus TCAD workflow. This allows designers to simulate silicon modulators, for example, by passing complex index profiles from Sentaurus Device to BeamPROP for optical simulation, or to simulate waveguide photodetectors by passing absorption profiles from FullWAVE or BeamPROP to Sentaurus Device for electronic simulation.

RSoft tools are seamlessly integrated into Synopsys Sentaurus Workbench

Figure 1. RSoft tools are seamlessly integrated into Synopsys Sentaurus Workbench

Industry-Leading Optoelectronic Analysis with These Key Benefits

The interface between industry-leading tools Sentaurus TCAD and RSoft photonic design software provides a powerful, unique approach for modeling and analyzing optoelectronic devices.

  • Run comprehensive simulations
    • Sentaurus TCAD is the gold standard tool for semiconductor process and device simulation
    • The RSoft products provide industry-leading photonic design automation (PDA) tools at the device, circuit and system levels
    • The RSoft products are seamlessly integrated into Sentaurus Workbench to provide a complete, integrated optoelectronic analysis workflow
    • All passive RSoft simulators can be included in a simulation design flow for in-depth photonic device analysis that considers the full 3D spatial behavior of the EM field and electron device characteristics
  • Save time by drawing exact geometry once
    • Exact Sentaurus TCAD geometry used by the RSoft tools allowing for efficient sub-cell gridding (sometimes called conformal meshing)
    • Other approaches require either manually converting the geometry for optical simulation resulting in inaccuracies, or drawing geometry in both TCAD and optical tools.
    • Includes exact process effects in optical simulations; these effects are not easily drawn in other optical CAD tools
  • Avoid messy file format conversions and streamline analysis with native bi-directional data transfer between the Synopsys RSoft products and Sentaurus TCAD tools
    • RSoft reads and writes native Sentaurus TCAD data files, which can be used in Sentaurus TCAD steps with no data conversion or extra scripting needed

Example Design Flow: 3D Free-Carrier Si Modulator

The goal:

Model and analyze a phase shifter for use in a 3D free-carrier silicon modulator with longitudinal P-N junctions. The structure varies in both transverse and longitudinal directions and requires simulation by a 3D electronic solver such as Sentaurus TCAD.

Simulation tools used:

Sentaurus Structure Editor is used to model the modulator structure, doping calculation and electronics. Sentaurus Device Simulator is used for 3D electronic simulation to calculate properties such as electron density, hole density, and complex refractive index perturbation. This calculation was performed at several bias points. Finally, RSoft BeamPROP is used to perform the optical beam propagation analysis at each bias point to calculate the resulting phase shift. 

Silicon modulator modeled in Sentaurus Structure Editor

Figure 2. Silicon modulator modeled in Sentaurus Structure Editor

The result:

The result, shown in Figure 3, shows the guided mode in the waveguide, the amplitude and phase of the propagating field, and the phase shift vs. bias. The phase shift can be used to calculate the properties of the phase shifter such as Vπ, the figure of merit of the modulator.

RSoft BeamPROP simulation results for silicon modulator

Figure 3. RSoft BeamPROP simulation results for silicon modulator

Example Design Flow: 3D SiGe Waveguide PhotoDetector

The goal:

Calculate the I-V curve for a Ge photodetector integrated on top of an Si waveguide separated by a thin SiON layer. A taper is used to convert the optical mode from Si to Ge. Roughly 30 tungsten (W) pillars are alternately connected to one of two bias contact. SiO2 surrounds the entire structure.

Simulation tools used:

Sentaurus TCAD tools are used to draw the structure geometry, shown in Figure 4.

SiGe photodetector modeled in Sentaurus Device

Figure 4. SiGe photodetector modeled in Sentaurus Device

The geometry is then passed to the RSoft tools, which calculate the 3D optical generation profile within the structure. RSoft BeamPROP or FullWAVE tools can be used to calculate the optical generation profile. The Sentaurus TCAD tools then perform the electronic simulation to calculate the I-V curve.

The result:

See Figure 5 for the photodetector analysis results from the RSoft and Sentaurus TCAD tools.

Structure seen in the RSoft CAD
Optical Generation Profile calculated by RSoft
I-V curves calculated by Sentaurus TCAD

Figure 5 a) Structure seen in the RSoft CAD; b) Optical Generation Profile calculated by RSoft; c) I-V curves calculated by Sentaurus TCAD.

BeamPROP, based on the BPM algorithm, offers an extremely fast alternative to FDTD simulation with reasonable accuracy. Figure 6 shows a comparison of I-V curve results using optical data from FullWAVE (FDTD) and BeamPROP (BPM). The BPM results are similar to the FDTD results and are obtained approximately 50x faster than FDTD.

Comparison of I-V curve results using optical data from FullWAVE (FDTD) and BeamPROP (BPM).

Figure 6. Comparison of I-V curve results using optical data from FullWAVE (FDTD) and BeamPROP (BPM).

Learn More About the RSoft Tools

  • BeamPROP based on the Beam Propagation Method (BPM) for the design and simulation of integrated and fiber-optic waveguide devices and circuits
  • FullWAVE with finite-difference time-domain (FDTD) analysis to perform full-vector simulations of photonic structures
  • Complete index of RSoft tools