# Difference between 2D and 3D CHARGE simulations

#1

What is the diference between 3D CHARGE and 2D (y normal, x normal and z normal) CHARGE in Device.

Geometry building issue in 3D simulation for DEVICE
Laser heating triple-junction solar cell
#2

The 3D CHARGE simulation in DEVICE simulates a complete 3D structure (inside the simulation volume) and the results are provided for the entire structure. For example it will report the total current in the system in units of Amp.

The 2D CHARGE simulations (x normal, y normal, and z normal) uses any uniformity a structure might have in a particular dimension to perform a 2D simulation on a cross-section. The reported results are calculated by assuming that the system has a length equal to the “norm length” in the third dimension. The “norm length” is a property of the solver region and can be set to any desired value. By default “norm length” is set to 1 cm (10000 micron) so the values will be reported for 1 cm width of the device.

#3

Hi Aalam, I understand that the current I will be normalized by this norm length. How about the current density? what is its unity? When I change the norm length, current density seems not changing. Thank you.

#4

Hi @yongmingtu2012, if you are talking about the current density reported by the CHARGE solver (as part of the “charge” dataset) then the unit is always A/cm^2 as mentioned in this KB page: Simulation - CHARGE.

#5

A post was split to a new topic: Relation between potential in the band diagram and applied voltage under forward bias