Plotting Schottkly diode I-V chracteristics

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))))

Answer 1

[Srijith Kasaragod]

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))));

[Ranjan Kandasamy]

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]

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.