I am self studying Matlab and I want to create a plot with electron modility and inverse temperature as the picture shows:

I have created a code in matlab but I do not see the line in the plot .Why ?

% Constants
k = 1.38e-23;  % Boltzmann's constant (J/K)
Eg = 1.12;     % Energy band gap of silicon (eV)
A = 2.5e19;    % Constant for intrinsic carrier concentration calculation
Nc = 2.8e19;   % Effective density of states in conduction band (cm^-3)
Nd = 1e16;     % Doping concentration (cm^-3)

% Temperature range
T = linspace(100, 1000, 100);  % Temperature range from 100 K to 1000 K

% Electron concentration for n-type doping
n = Nc * exp(-(Eg./(2*k*T))) .* (Nd./(Nc.*exp(-(Eg./(2*k*T)))) + 1).^0.5;

% Calculate ln(n)
ln_n = log(n);

% Calculate 1/T
inv_T = 1 ./ T;

% Plot
plot(inv_T, ln_n, 'r', 'LineWidth', 2);
xlabel('1/T');
ylabel('ln(N_D)');
title('ln(Electron Concentration) vs. 1/T for Silicon');
grid on;

Does anyone knows ?