The layer table is the device. Each row is a layer, read in growth order, and eight columns describe it — though most structures need only the first five.
01One row per layer
Rows run from the outside of the device inwards: the top row is the surface — the side the boundary condition applies to — and the bottom row is deepest. Add rows with Add Layer, put one above the current selection with Insert Layer, and remove it with Delete Layer.
A layer needs, at minimum, a material and a thickness. Everything else can stay blank and sensible defaults are used.
02The eight columns
- Material — a name from the materials database. Spelling is forgiving of case, and common aliases are accepted.
- Thickness (nm) — the layer thickness in nanometres.
- Fraction (%) — for an alloy, the mole fraction in percent. An In0.53Ga0.47As layer is entered as 53, not 0.53. Leave blank for a binary material.
- p-doping (cm⁻³) — acceptor concentration, e.g. 1e18.
- n-doping (cm⁻³) — donor concentration. Do not put a value in both doping columns for the same layer: enter the net doping in whichever column applies. Filling both is rejected with an error message rather than silently resolved, so you will know about it.
- Dopant depth (eV) — optional binding energy of the dopant with respect to the appropriate band edge (conduction band for donors or valence band for acceptors). Leave blank to use the material default, or to select fully ionised dopants.
- Mobility (cm²/Vs) — optional; used for the transport reporting. Blank uses the material’s own value.
- Contact Voltage (V) — marks a layer as a terminal and sets its voltage, only used in contact-bias mode. For a p–n structure, forward bias means the p-side contact is positive relative to the n-side.
The composition and doping columns also accept gradients, written as two values separated by a slash — see Composition and Doping Gradients.
03Blank is not the same as zero
This distinction may not be obvious, but it is deliberate.
Leave a doping cell blank and the material’s own built-in doping is applied — some materials are natively doped as grown. Enter 0 and you force a genuinely undoped, intrinsic layer, overriding that default. The two give different devices, so if you want an intrinsic spacer, type the zero rather than leaving the cell empty.
The behaviour is governed by Use material default doping, in the Simulation parameters panel, which is on by default. It only ever applies when both doping cells of a layer are blank; any explicit entry — including zero — always wins.
04Repeating a block of layers
For a superlattice or a multi-period stack you do not need to type every period. Put a row containing 10*{ above the block and a row containing } below it, and those layers are repeated ten times. The marker rows hold nothing else — just the brace text in the Material column.
Blocks may be nested, so a repeated group can itself contain a repeated group.
05The substrate row
A final row reading substrate: GaAs (or any material) adds a semi-infinite rear reference reservoir. It is not meshed and takes no thickness — it exists to anchor the far side of the structure. A plain substrate row with no material after the colon is simply ignored. Details are in The Substrate Row.
Software Utilities 