TheAlgorithms/Python · error · ValueError

Electron concentration cannot be negative in a semiconductor

Q: What causes "Electron concentration cannot be negative in a semiconductor" in TheAlgorithms/Python?

Fix the sign of electron_conc at the source; it must be >= 0.

Error message

Electron concentration cannot be negative in a semiconductor

What it means

Thrown by carrier_concentration() when electron_conc < 0 while the zero-count precondition is satisfied. Negative carrier concentrations are non-physical (concentrations are per-volume counts), so the library refuses them before applying the mass-action law n*p = ni^2.

Source

Thrown at electronics/carrier_concentration.py:46

        ...
    ValueError: You cannot supply more or less than 2 values
    >>> carrier_concentration(electron_conc=-1000, hole_conc=0, intrinsic_conc=1200)
    Traceback (most recent call last):
        ...
    ValueError: Electron concentration cannot be negative in a semiconductor
    >>> carrier_concentration(electron_conc=0, hole_conc=-400, intrinsic_conc=1200)
    Traceback (most recent call last):
        ...
    ValueError: Hole concentration cannot be negative in a semiconductor
    >>> carrier_concentration(electron_conc=0, hole_conc=400, intrinsic_conc=-1200)
    Traceback (most recent call last):
        ...
    ValueError: Intrinsic concentration cannot be negative in a semiconductor
    """
    if (electron_conc, hole_conc, intrinsic_conc).count(0) != 1:
        raise ValueError("You cannot supply more or less than 2 values")
    elif electron_conc < 0:
        raise ValueError("Electron concentration cannot be negative in a semiconductor")
    elif hole_conc < 0:
        raise ValueError("Hole concentration cannot be negative in a semiconductor")
    elif intrinsic_conc < 0:
        raise ValueError(
            "Intrinsic concentration cannot be negative in a semiconductor"
        )
    elif electron_conc == 0:
        return (
            "electron_conc",
            intrinsic_conc**2 / hole_conc,
        )
    elif hole_conc == 0:
        return (
            "hole_conc",
            intrinsic_conc**2 / electron_conc,
        )
    elif intrinsic_conc == 0:
        return (

View on GitHub (pinned to f5988cc097)

Solutions

Fix the sign of electron_conc at the source; it must be >= 0.
If the value comes from a noisy measurement, clamp or validate it before calling: raise if electron_conc < 0 rather than letting the library do it.
Re-derive the value: for n-type material electron_conc should equal N_D (positive donor density).

Example fix

# before
carrier_concentration(electron_conc=-1e15, hole_conc=0, intrinsic_conc=1e10)

# after
carrier_concentration(electron_conc=1e15, hole_conc=0, intrinsic_conc=1e10)

Defensive patterns

Strategy: validation

Validate before calling

if electron_conc < 0:
    raise ValueError("electron_conc must be >= 0")
result = carrier_concentration(electron_conc, hole_conc, intrinsic_conc)

Prevention

Carrier concentrations are counts — sanitize with abs() only when sign is a known convention.
Validate measured data ranges before passing to physics functions.

When it happens

Trigger: carrier_concentration(electron_conc=-100, hole_conc=0, intrinsic_conc=1200) — exactly one zero but a negative electron concentration.

Common situations: Sign errors from subtraction-based derivations (e.g. n = N_D - N_A computed backwards); sensor/instrument data with negative noise around zero; CSV imports where a minus sign slipped in.

Related errors

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/5387c94cfa6d4872. Report an issue: GitHub.