Junction Capacitance in a GaAs Photodiode

AI Thread Summary
The discussion centers on estimating the junction capacitance of a GaAs photodiode across varying bias voltages, with the user struggling to achieve expected results. They reference equations from a semiconductor physics textbook but find their calculations yield values significantly off from expectations, suspecting incorrect variable values. Other participants inquire about the specific photodiode model and expected capacitance, with one mentioning a previous calculation of 250pF at 0V. The user acknowledges the need to correct their variable values but has not yet provided detailed calculations for review. Clarification on the equations and accurate variable values is sought to resolve the discrepancies in capacitance calculations.
GraemeC
Messages
3
Reaction score
0
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

Junction1.PNG


with
ε0 = permittivity of free space
εGgAs = GaAs dielectric constant
μ = Mobility of electrons
ρ = resitivity
Vbi = built-in voltage
VA = Bias voltage (in my case 0 - 5V)
A = photodiode area (in my case 0.3μm2)

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.
 
Engineering news on Phys.org
Welcome to PF.
What is the make and model of the photodiode ?
What capacitance do you expect ?
 
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
 

Thread 'Underwater piezoelectric sensor array receive sensitivity'

Hi all I have some confusion about piezoelectrical sensors combination. If i have three acoustic piezoelectrical sensors (with same receive sensitivity in dB ref V/1uPa) placed at specific distance, these sensors receive acoustic signal from a sound source placed at far field distance (Plane Wave) and from broadside. I receive output of these sensors through individual preamplifiers, add them through hardware like summer circuit adder or in software after digitization and in this way got an...
View full post »

Thread 'Following up on the recent thread about Earth Resistance measurements'

I have recently moved into a new (rather ancient) house and had a few trips of my Residual Current breaker. I dug out my old Socket tester which tell me the three pins are correct. But then the Red warning light tells me my socket(s) fail the loop test. I never had this before but my last house had an overhead supply with no Earth from the company. The tester said "get this checked" and the man said the (high but not ridiculous) earth resistance was acceptable. I stuck a new copper earth...
View full post »

Thread 'Question about bonding ground and neutral'

I am not an electrical engineering student, but a lowly apprentice electrician. I learn both on the job and also take classes for my apprenticeship. I recently wired my first transformer and I understand that the neutral and ground are bonded together in the transformer or in the service. What I don't understand is, if the neutral is a current carrying conductor, which is then bonded to the ground conductor, why does current only flow back to its source and not on the ground path...
View full post »

Similar threads

PIN photodiode forward bias capacitance
Replies
12
Views
4K
Calculate Bandgap Voltage for GaAs Photodiode: 5V Reverse Bias
Replies
1
Views
4K
Question about Parasitic capacitances and physical grounds
Replies
5
Views
4K
BJT transistor analysis: common emitter confusion
Replies
5
Views
3K
What's wrong in my LTspice simulation of an Op-Amp integrator circuit?
Replies
9
Views
6K
Complete Noise Analysis: to find the minimum detectable signal
Replies
9
Views
3K
Will this circuit protect my MOSFET from ESD?
Replies
6
Views
9K
I Are solar cells operated under any kind of bias or not?
Replies
3
Views
6K
Find the charge on the plates of a parallel-plate capacitor w/ dielectric
Replies
3
Views
2K
Understanding PN Junction Diodes: Vbi & Measuring Voltage
Replies
16
Views
11K

Hot Threads

Recent Insights

Back
Top