1. Waveguide Ge-PD Simulation
Jeong-Min Lee

2. Ge-PD Simulation Lumerical Device Lumerical FDTD
Current-voltage characteristic
Band structure
Charge (Jn, Jp, …)
Doping (NA, ND, ...)
Electrostatics (E, V, …)
Mobility (μn, μp, …)
Lumerical FDTD
Photo-generated carriers

3. Ge-PD Structure <Top-view> <Cross-section>
Doping concentration
P-type Si: 2x1018 /cm3 (constant doping)
i-Ge: 2x1013 /cm3 (constant doping)
N-type Ge: ~ 5x1018 /cm3 (diffusion doping)

4. Procedure Configure materials Draw & configure 3-D structure of Ge-PD
Draw & configure doping layers
P-type, intrinsic, n-type
Draw & configure device region
Simulation area
Define & configure electrical contacts
Cathode, anode
Device simulation
Electric field, dark current simulation
FDTD simulation
Photo-generated carrier calculation
Photocurrent, responsivity simulation

5. Material Setting: Ge

6. Oxide

7. Silicon Substrate

8. Silicon Taper

9. Ge

10. Cathode

11. Anode
& 5.3 (another anode)

12. P-Type Si (Constant Doping)

13. Intrinsic Ge (Constant Doping)

14. N-Type Si (Diffusion Doping)

15. Device Region: Simulation Area
 2D simulation (/μm)
 PD length

16. Device Region Setting (Simulation Area)

17. Electrical Contact Setting

18. Simulation Results: Doping Profile

19. Simulation Results: Electric Field Distribution
At VR = 2V

20. Simulation Results: Cathode Current (Dark)

21. Simulation Results: Anode Current (Dark)

22. FDTD: Structure
1. Draw structure

23. FDTD Simulation Region1 2 3 4

24. Source (1/2): Mode Source

25. Source (2/2): Mode Select4 3 5

26. Generation Rate 1 2 4 5 3
6. Click Run

27. Edit Code
sourceintensity(f)  sourcepower(f)

28. Make Generation Rate File
Make ‘CW_generation.mat’ file in working directory

29. Device: Import Generation Rate1 2 3

30. Simulation Results: Photocurrent (Cathode)

31. Simulation Results: Responsivity
Load ‘Bias vs. Responsivity.lsf’
Run

32. Code Bias vs. Responsivity.lsf Pin=1e-3; # Watts
I=-2*getdata("Device region", "anode.I");
V=linspace(0,4,5);
Resp=I/Pin;
plot(V,I*1e6,"photo detector bias voltage(V)","I_(illumination) uA ");
plot(V,Resp,"photo detector bias voltage(V)","Responsivity (A/W) ");

33. Exercise Draw same structure of Ge p-i-n PD.
Doping concentration conditions:
P-type: 2x1019 /cm3
Intrinsic: 2x1013 /cm3
N-type: 5x1019 /cm3 (ref concentration: 1x1017 /cm3)
Plot doping profiles (NA, ND).
Plot electric-field profiles at 1- and 4-V reverse bias voltage.
Plot dark current, photocurrent, and responsivity according to reverse bias voltages from 0 to 4V.