code: def plot_carriers(self, temp=300):
          
          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
docs: Plot the carrier concentration in function of Fermi level
  
          Args:
              temp: the temperature
  
          Returns:
              a matplotlib object