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

Research Area(s):



View Research Quadslide


  • 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.

Key Results

  • 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.

Future Work

  • 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%.