Development and Characterization of Metal Contacts for Graded Composition InGaN Solar Cells
Student: Reem Alhelais
Degree: M.S., May 2020
Major Professor: Dr. Morgan Ware
The III-nitrides pose unique challenges in the fabrication of solar cells particularly due to the high resistivity of the material and the unavailability of metals to make contacts.
A big challenge in making solar cells out of III-Nitride materials is to form a low resistance ohmic contact with InGaN graded layer because of the difference between the electron affinity of InN and GaN that is limiting the devices’ performance.
Study contacts on the III-nitride solar cell structure to make Ohmic contact with graded layer with different annealing temperature.
- Because wet etching of these materials is difficult, dry etching by ICP is preferred by using both chlorine (Cl2) and boron trichloride (BCl3) which are reactive gases on III-nitride materials.
- Deposit various metals to make ohmic contact beginning with Ni/Au, and Cr/Au.
- Optimize the contacts by varying annealing times, and temperatures because annealing is the mostly used method for lowering the barrier height at the interface.
- Fabricated InGaN graded layer to study ohmic contact.
- TLM can be used to measure contact resistance, R_C, and the sheet resistance, and specific contact resistivity.
The transmission line method (TLM) is the most common way to characterize the contact resistance of the metal contacts to semiconductor solar cells.
Use new metals to make ohmic contacts on graded InGaN sample to achieve the lower contact resistance R_C.
Grow InGaN with In composition higher than 30%.