As shown, two Silicon (Si) abrupt p-n junction diodes are fabricated with uniform donor doping concentration of N _D1=10¹⁴ cm⁻³ and N_D2=10¹⁶cm^-3 in the n-regions of the diodes, and uniform acceptor doping concentration of N _A1=10¹⁴ cm⁻³ and N_A2=10¹⁶cm^-3 in the p- regions of the diodes, respectively. Assuming that the reverse bias voltage is >> built-in potentials of the diodes, the ratio C ₂ C₁ of their reverse bias capacitances for the same applied reverse bias, is _______.