To find the ratio of Nd/N2, we need to consider the current flow in the depletion region of an ideal silicon junction diode.

1. Current flow in the depletion region:
In an ideal silicon junction diode, the total current flowing in the depletion region is the sum of the electron current (Ie) and the hole current (Ih). Since we are given that 80% of the current is carried by electrons, we can express this as:
Ie = 0.8 * Itotal
Ih = 0.2 * Itotal

2. Calculation of the diffusion current:
The diffusion current is given by the equation:
Idiff = q * (Dp * p0 / Lp + Dn * n0 / Ln)
where q is the charge of an electron, Dp and Dn are the diffusion coefficients, and p0 and n0 are the equilibrium concentrations of holes and electrons respectively in the depletion region.

3. Calculation of the hole and electron concentrations:
In thermal equilibrium, the equilibrium concentrations of holes and electrons are related by the equation:
p0 * n0 = ni^2
where ni is the intrinsic carrier concentration.

4. Calculation of the intrinsic carrier concentration:
The intrinsic carrier concentration is given by the equation:
ni^2 = Nc * Nv * exp(-Eg / (2 * k * T))
where Nc and Nv are the effective densities of states in the conduction and valence bands respectively, Eg is the energy gap of silicon, k is the Boltzmann constant, and T is the temperature in Kelvin.

5. Calculation of the depletion region width:
The depletion region width (W) is given by the equation:
W = sqrt((2 * εs * (Vbi - V)) / (q * (N1 + N2)))
where εs is the permittivity of silicon, Vbi is the built-in potential, V is the applied voltage, and N1 and N2 are the doping concentrations on the p-side and n-side of the junction respectively.

6. Calculation of the ratio of Nd/N2:
Finally, we can calculate the ratio of Nd/N2 using the equation:
Nd/N2 = (W - x) / x
where x is the width of the depletion region in the n-side.

By substituting the given values and solving the above equations, we can find that the ratio of Nd/N2 lies between 2.5 and 2.6.

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