BIAS

The bias command carries out steady state device analysis.

• SYSTEM = (s)
• INITIAL = (l)
• ELECTRODE = (s)
• NSTEPS=(i)
• VOLTAGE=(r)
• VSTEP=(r)
• TIME=(r)
• TEMPERATURE=(r)

The following list itemizes the valid keywords, their units and their meaning.

SYSTEM: [string]

system of equations to use. One set must be chosen. Currently supported: newton0, newton1e, newton1h, newton2, and any user-defined system of equations

INITIAL: [logical]

the INITIAL solution is chosen, all biases are reset to zero, the potential is set to the charge neutral solution and the carriers adjusted accordingly. Then the system of equations is solved. Other bias parameters are ignored.

ELECTRODE: [string or string array]

BIAS command allows one applied bias at a time to be modified. The ELECTRODE parameter defines which electrode is being modified. The string refers to a name defined either on a boundary command or read from a previous grid. More than one electrode can be specified using a string array, e.g.,

electrode=gate,drain

NSTEPS: [integer]

number of bias increments to be taken. May be omitted if there is just one.

VSTEP: [real or real array (volts)]

voltage step to be taken for each bias step. If the bias values of multiple electrodes are being changed, use a real array, e.g.,

vstep=0.5,1.0

where there is one value for each electrode value being changed.

TIME: [real (seconds)]

time interval for a transient solution.

VOLTAGE: [real or real array (volts)]

a single step is desired, specify VOLTAGE instead of VSTEP. If the bias values of multiple electrodes are being changed, use a real array, e.g.,

voltage=0.5,1.0

where there is one value for each electrode being changed.

TCELSIUS: [real (degrees Celsius)]

temperature at which the simulation is performed. Default is 26.85C (300K).

TKELVIN: [real (degrees Kelvin)]

temperature at which the simulation is performed. Default is 300K.

VINIT: [real or real array (volts)]

voltage of a voltage ramp. Used in one of these combinations: vinit, vfinal, nstep; or vinit, vstep, nstep. If the bias values of multiple electrodes are being changed, use a real array, e.g.,

vinit=0.5,1.0

where there is one value for each electrode being changed.

VFINAL: [real or real array (volts)]

voltage of a voltage ramp. Used in one of these combinations: vinit, vfinal, nstep; or vinit, vstep, nstep.

If the bias values of multiple electrodes are being changed, use a real array, e.g.,

vinit=0.5,1.0

where there is one value for each electrode being changed.

Examples:
First bias statement needs the ``initial'' keyword:
bias system=silicon_poisson initial
To solve for a particular bias value:
bias system=silicon_dd voltage=0.5 elec=anode
To solve for a series of bias values:
bias system=silicon_dd vstep=0.1 nstep=20 elec=gate
To step biases on two electrodes at once:
bias system=silicon_dd vinit=0.1,0.1 vfinal=0.5,0.5 nstep=4 elec=gate,drain

Less Used BIAS Keywords

MIN.BACKSTEP

a given bias step does not converge, the size of the voltage step will be reduced until it does. However, ``MIN.BACKSTEP'' is the minimum fraction of the original voltage step that is allowed before the BIAS command terminates.

TEMPERATURE: [real (degrees celsius)]

temperature at which the simulation is performed. Default is 26.85C (300K).

VOLT.EXPR: [string or string array]

expression.

FSTHARMONICS

balance analysis parameter.

SNDHARMONICS

balance analysis parameter.

FSTFREQUENCY

balance analysis parameter.

SNDFREQUENCY

balance analysis parameter.

FSTAMPLITUDE

balance analysis parameter.

SNDAMPLITUDE

balance analysis parameter.