Study of Palladium/Gallium Antimonide Rections and Ohmic Contacts to n-type Gallium Antimonide

Open Access
- Author:
- Robinson, Joshua Alexander
- Graduate Program:
- Materials Science and Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 06, 2005
- Committee Members:
- Suzanne E Mohney, Committee Chair/Co-Chair
Elizabeth C Dickey, Committee Member
Zi Kui Liu, Committee Member
S Ashok, Committee Member - Keywords:
- Ohmic Contact
Palladium
GaSb - Abstract:
- Antimonide-based compound semiconductors show great promise for optoelectronic and high speed electronic devices. GaSb, and related ternary and quaternary alloys, have emerged as critical materials for infrared lasers, thermophotovoltaic devices, solar cells, and transistors. To ensure device reliability and performance, ohmic contacts with low specific contact resistance, good thermal stability, and excellent surface and interfacial morphology are required. In recent years a move from traditional Au-based contacts to Pd-based contacts has improved thermal and morphological stability of contacts to Sb-based semiconductors. The characterization and understanding of how a Pd thin film interacts with GaSb is essential to further improve contacts to n-GaSb. Research presented in this thesis yields phase formation and reaction morphologies important for Pd-based contacts to n-GaSb. A Pd/GaSb thin film study identifies phase formation necessary for the solid phase regrowth mechanism for ohmic contact formation and the ohmic behavior of a Pd(50 nm)/GaSb contact. A subsequent study of the Pd-rich region of the Pd-Ga-Sb phase diagram verifies the existence of several Pd-rich ternary phases observed in the thin film research. Next, research focused on the engineering of Pd-bearing ohmic contacts that include indium. Two low resistance ohmic contacts will be presented that exhibit electrical properties comparable to In-based contacts reported in the literature. However, these contacts improve upon previously reported contacts to n-GaSb by offering improved surface morphology, reduced reaction depth, and improved thermal stability. A Pd<sub>3</sub>In<sub>7</sub>/WSiN/Au contact presented here exhibits unmatched thermal stability and ultra-shallow reaction depths. Finally, the effect of surface treatments will be presented as a means to reduce the specific contact resistance, improve reaction uniformity, and understand Sb-based semiconductor passivation. It will be shown that by replacing a conventional surface treatment that includes a deionized water rinse with a dilute ammonium sulfide solution rinse, it is possible to rid the surface of any contamination layers, reduce the specific contact resistance of ohmic contacts to n-GaSb, and improve reaction uniformity.