def emitter_injection_efficiency(i_en=0,i_e=1):
    """
    The emitter injection efficiency measures the fraction
    of the emitter current carried by the desired electrons
    or holes in a NPN or PNP device. The default is for a
    NPN device.

    Parameters
    ----------
    i_en : float, required
        Electron emitter current. The default is 0.
    i_e : TYPE, optional
        Emitter current. The default is 1.

    Returns
    -------
    A float value corresponding to the emitter injection efficiency

    """
    gamma = i_en / i_e
    return gamma