I am trying to get an estimation the junction capacitance of my GaAs Photodiode with respect to varying bias voltages. My Semiconductor Physics online textbook gives the following equations with ε_{0} = permittivity of free space ε_{GgAs} = GaAs dielectric constant μ = Mobility of electrons ρ = resitivity V_{bi} = built-in voltage V_{A} = Bias voltage (in my case 0 - 5V) A = photodiode area (in my case 0.3μm^{2}) Whenever, I work through the calculations I get answers that are many orders of magnitude off what I expect I think the main issue is just getting the correct values(in the correct units) for each of the variables as I have been pulling them in from different sources. Any help would appreciated.
It's custom part. My colleague did a calculation a while back and came up 250pF at 0V I'm getting femtoFarads which is definitely not right!
You haven't shown us your work. You seem to have diagnosed your problem is, but haven't taken the step of fixing it. What exactly are you asking for?
Confirmation that the equations I've given are correct and then values for ε0 = permittivity of free space εGgAs = GaAs dielectric constant μ = Mobility of electrons ρ = resitivity Vbi = built-in voltage