Plotting Schottkly diode I-V chracteristics

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I am trying to plot current density vs voltage for the schottky diode.
This is my code so far:
clc
clear all
n = 1.02; %Ideality factor
A = 33.65; %Richardson constant
q = 1.602*10^-19; % electron charge
K = 1.38*10^-23; %Boltzmann constant
T = 300; % Absolute temperature
phi_b = 0.28; %Barrier Height
V = 0:0.2:2;
J_0 = A* (T* T)* exp((-q* phi_b)./(K* T));
J = J_0 * exp((q* V)./(n* K* T))* (1 - (exp(-q* V)./(K* T)));
plot(V, log(J ./(1 - exp(-q* V)/(k *T))))

Accepted Answer

Srijith Kasaragod
Srijith Kasaragod on 2 Sep 2021
Edited: Srijith Kasaragod on 7 Sep 2021
Assuming correctness of parameters and equations, error exists only in final 2 lines of code. Multiplication to compute J must be elementwise multiplication rather than matrix multiplication. Also Botzmann constant is saved as variable 'K' and not 'k'. Making these two changes generates the plot.
J = J_0* exp((q* V)./(n* K* T)).* (1 - (exp(-q* V)./(K* T)));
plot(V, log(J ./(1 - exp(-q* V)/(K *T))));
  2 Comments
Ranjan Kandasamy
Ranjan Kandasamy on 2 Sep 2021
Edited: Ranjan Kandasamy on 2 Sep 2021
How do I know if I need to do matrix multiplication or element-wise multiplication? I tried doing what you said and still get this error:
Error using *
Incorrect dimensions for matrix multiplication. Check that the number of columns in the first matrix matches the number of rows in the second matrix. To perform elementwise
multiplication, use '.*'.
Error in ss (line 11)
J = J_0* exp((q* V)./(n* K* T))* (1 - (exp(-q* V)./(K* T)));
Okay, I changed the above expression to J = J_0.* exp((q* V)./(n* K* T)).* (1 - (exp(-q* V)./(K* T))) and it works, but again how do I know where to use element-wise operators?
Srijith Kasaragod
Srijith Kasaragod on 3 Sep 2021
Edited: Srijith Kasaragod on 20 Sep 2021
You have 11 voltage values in array 'V'. Your requirement is to find corresponding 11 current values and plot the I-V characteristics. The two terms being multiplied in line 11 are both of size 1-by-11. To get the required current values, you have to perform element-wise multiplication between these two arrays. Matrix multiplication would give either 1-by-1 or 11-by-11 matrix according to the order of matrix multiplication, which is not the desired output.

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