minor bugfix

code/semiconductors.py

@@ -46,7 +46,6 @@ def plot_doping():
     n_F = 1/(np.exp(2*(E - E_F)) + 1)
     g_e = m_e * sqrt_plus(E - E_C)
     g_h = m_h * sqrt_plus(E_V - E)
-    sqrt_plus = lambda x: np.sqrt(x * (x >= 0))
     ax.plot(E, g_h, label="$g_e$")
     ax.plot(E, g_e, label="$g_h$")