def plot_carriers(self, temp=300):
        """
        Plot the carrier concentration in function of Fermi level

        Args:
            temp: the temperature

        Returns:
            a matplotlib object
        """
        import matplotlib.pyplot as plt
        plt.semilogy(self._bz.mu_steps,
                     abs(self._bz._carrier_conc[temp] / (self._bz.vol * 1e-24)),
                     linewidth=3.0, color='r')
        self._plot_bg_limits()
        self._plot_doping(temp)
        plt.xlim(-0.5, self._bz.gap + 0.5)
        plt.ylim(1e14, 1e22)
        plt.ylabel("carrier concentration (cm-3)", fontsize=30.0)
        plt.xlabel("E-E$_f$ (eV)", fontsize=30)
        plt.xticks(fontsize=25)
        plt.yticks(fontsize=25)
        return plt