I want to use a commercial schottky diode to extract the workfunction of the metal used in it.
i have access to CV and IV tools.
the schottky diode has a guard ring as well, so how do i calculate the doping density in the guard ring as well as the drift region.
i have the CV, BV and peak current of the diode from the manufacturers datasheet.
Also, is there a fermi level pinning at the metal contact?
Dear Ashok,
There is no workfunction of the Schottky diode but are you said correctly later in your question there is work function of a material including metals. Since the Schottky diode is built by an MS contact then one defines for its metal a workfucntion phi. If you review the theory of operation of the Schottky diode you can know how would you determine the metal workfunction wf of the Schottky diode by measuring its I-V characteristics or its its small signal C-V characteristics.
For the the I-V characteristics:
The I-V characteristics of the Schottky diode can be expresses by:
I= A T^2 exp - phi /Vt ( exp V/Vt _1) = Is ( exp V/Vt _1)
where A is the effective Richardson constant, T is the temperature in Kelvin, Vt the temperature equivalent voltage , phi is the barrier height and V is the applied voltage. From the above equation knowing T one can determine phi from the Is.
After calculating phi one can then calculate the work function of the metal wf from the relation wf= phi+ X, where X is the electron affinity of the semicondcutor used to produce the Schottky diode.
The barrier height phi can be obtained directly from the plot of 1/C^2 versus V where C is the small signal capacitance of the diode is normally measured in reverse biasing. Then one can get the barrier height phi from the relation:
phi= Vi + Vn where Vi is the intercept of the straight line with the voltage axis and Vn is the fermi potential refereed to the conduction band edge It depends on the doping and semicondcutor that is Nd= Nc exp -Vn/Vt , where Nd is the donor concentration, Nc is the effective density of sates in the conduction band and Vt is the temperature equivalent voltage= 25.6 mV at 300K.
The reference is S.M Sze, physics of semicondcutor devices.
These relationships valid if there is no heavy traps at the surface of semiconductor which can lead to the fermi level pinning and so the barrier height will be no longer determined by the work function of the metal.
The other thing is that if one post heat the metal at relatively elevated temperature silicides will formed which has different work function than the metal.
Best wishes
I have no answer to this question, another time I will want to answer you. It's a good question@@
Thanks for the question and the answer. Is there a way for finding electron affinity of unknown semiconductor?
- Badges
- Science method
- Similar topics
- Methodology
- Crystallography
- X-ray Diffraction