Sheet Resistance and Transport

Reading results

The Layer Transport tab turns the equilibrium carrier profile into a lateral sheet resistance — a parallel-conduction estimate that shows which layer actually carries the current.

01The value at the top

The tab opens with a single bold figure, Structure sheet resistance, in ohms per square (Ω/sq). This is the sheet resistance the whole stack would present to a current flowing along the layers. Sheet resistance is independent of the patterned size: multiply it by the number of squares in a path (its length divided by its width) to get an actual resistance in ohms.

The layers conduct in parallel, so their sheet conductances add and the structure value is one over that sum. It is therefore always lower than the most conductive single layer — adding a poorly conducting layer can only help.

02The per-layer table

Below the total, the calculation is broken down into individual layers :

• Material and Thickness (nm) — the layer, with its alloy fraction shown where it applies.
• Electron sheet density (cm⁻²) and Hole sheet density (cm⁻²) — the free carriers in that layer, integrated through its thickness.
• Electron mobility (cm²/V·s) and Hole mobility (cm²/V·s) — the mobilities used for the two carriers.
• Current share (%) — the fraction of the whole structure’s sheet conductance that this layer provides. This is the column that names the channel: the layer with most of the share is the one carrying the current.
• Sheet resistance (Ω/sq) — the layer taken on its own. A layer with no free carriers reads ∞ and takes a zero share, which is the expected result for a depleted or barrier layer rather than a fault.
• Electron mobility source and Hole mobility source — each reads User or Database, so you can see at a glance which mobilities you set and which came from the materials database.

03Where the mobilities come from

The single Mobility column in the layer table sets the majority-carrier mobility: the electron mobility for an n-type layer, the hole mobility for a p-type one. The other carrier, and any layer whose cell you leave blank, takes its mobility from the materials database. That is why a doped layer often shows one User source and one Database source.

The mobility is used as a constant — there is no field or carrier-density dependence, and no separate treatment of a two-dimensional channel. Read the transport table as a clear first-order estimate of parallel conduction, not as a measured sheet resistance.