Someone help me to plot Ids vs Vds for HEMT AlGaN/GaN

i'm trinig to plot Ids vs Vds with matlab and i'm not having any result please check my code ;

Vth=2e-7;
Vs=1.5e-7;
Z=150e-6;
e=1.6e-19;
ep=8.85e-12;
mn=9.1e-31;
dd=30e-9;
di=7e-9;
x=1.05e-34;
u=1.257e-6;
L=150e-6;
Vgs=-4;
Vds=0;
Vdsat=Vgs-Vth+Vs-((Vgs-Vth)*(Vgs-Vth)+Vs*Vs);
if(Vdsat<Vds)
    Ids=2*Z*e*e*ep*mn*Vs/(2*(dd+di)*e*e*mn+ep*pi*x*x)*(((Vgs-Vth)*(Vgs-Vth)+Vs^0.5)-Vs);
end
if(Vdsat>Vds)
    Ids=2*u*Z*ep*e*e*mn/(L*(2*(dd+di)*e*e*mn+ep*pi*x*x))*((Vgs-Vth)*Vds-((Vds*Vds)/2));
end
figure; 
plot(Vds,Ids); 
xlabel('Vds  (V)'); 
ylabel('Ids  (mA/mm)'); 

Answer 1

[Aquatris]

I think what you are trying to do is vary Vds and see what Ids becomes. So here is a simple some modification for it using for loop. However you should try to vectorize the for loop for efficient code:

Vth=2e-7;
Vs=1.5e-7;
Z=150e-6;
e=1.6e-19;
ep=8.85e-12;
mn=9.1e-31;
dd=30e-9;
di=7e-9;
x=1.05e-34;
u=1.257e-6;
L=150e-6;
Vgs=-4;
Vds=-60:0.01:60; % generate a vector of interest
Vdsat=Vgs-Vth+Vs-((Vgs-Vth)*(Vgs-Vth)+Vs*Vs);
for i = 1:length(Vds) % loop through Vds and calculate corresponding Ids
   if(Vdsat<Vds(i))
      Ids(i)=2*Z*e*e*ep*mn*Vs/(2*(dd+di)*e*e*mn+ep*pi*x*x)*(((Vgs-Vth)*(Vgs-Vth)+Vs^0.5)-Vs);
   end
   if(Vdsat>Vds(i))
      Ids(i)=2*u*Z*ep*e*e*mn/(L*(2*(dd+di)*e*e*mn+ep*pi*x*x))*((Vgs-Vth)*Vds(i)-((Vds(i).*Vds(i))/2));
   end
end
figure;
plot(Vds,Ids);
xlabel('Vds  (V)');
ylabel('Ids  (mA/mm)');

[Stacy]

Can you please tell me how you are getting the unit of current as A/mm? As I can see in the code you didn't mention any division by 1000.

[Aquatris]

I have no idea about the units since non of the units are written for the variables. I just copied and modified the OP's code and modified to do what I assumed OP wanted to do.

Unless the units of each variable are given, it is hard to judge if this plot labels are correct ro not

Answer 2

[Mr. Pavl M.]

vectorized solution + units update:

clc
clear all
close all

Vth=2e-7;
Vs=1.5e-7;
Z=150e-6;
e=1.6e-19;
ep=8.85e-12;
mn=9.1e-31;
dd=30e-9;
di=7e-9;
x=1.05e-34;
u=1.257e-6;
L=150e-6;
Vgs=-4;
Vds=-90:0.01:60; % feasible span(region) of Drain-Source transistor potential, [V]
Vdsat=Vgs-Vth+Vs-((Vgs-Vth)*(Vgs-Vth)+Vs*Vs);

Ids=2*u*Z*ep*e*e*mn/(L*(2*(dd+di)*e*e*mn+ep*pi*x*x))*((Vgs-Vth)*Vds-((Vds.*Vds)/2));
Ids(Vdsat<Vds) = 2*Z*e*e*ep*mn*Vs/(2*(dd+di)*e*e*mn+ep*pi*x*x)*(((Vgs-Vth)*(Vgs-Vth)+Vs^0.5)-Vs);

figure;
plot(Vds,Ids);
xlabel('Vds  (V)');
ylabel('Ids  (A/mm)');

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