Discipline: Chemistry and Chemical Sciences
Subcategory: Materials Science
Alex Molina - Pennsylvania State University
Co-Author(s): Jeffrey Shallenberger, Pennsylvania State University, PA; Suzanne E. Mohney, Pennsylvania State University, PA
Despite the predominance of silicon in the microelectronics industry, germanium (Ge) has received attention as an alternative p-type channel material for metal oxide semiconductor field effect transistors, due to its higher hole mobility. To fabricate high-performance devices, the interface between Ge and the gate dielectric must be carefully prepared, with minimal etching/roughening and unintended interfacial contaminants . Moreover, novel nanostructures of Ge also require careful treatment of the surface (or passivation) to allow us to interrogate their electronic and optical properties. As opposed to wet etching, vapor phase processing allows for easier sample handling and reduced hazardous waste . In this investigation, hydrobromic acid (HBr) was used to remove the native oxide and passivate an undoped (100) Ge wafer with n-type conductivity and a resistivity of 50 Ω·cm, then the surfaces were examined using x-ray photoelectron spectroscopy (XPS). The Ge wafers were exposed to vapors above solutions of HBr of varying concentrations. Once treatment was complete, samples were immediately introduced into the XPS load lock, then transferred into the photoemission chamber with a base pressure of 3.75 x 10-10 Torr. The XPS system uses a monochromatic Al Kα x-ray source, and samples are inclined at an angle of 45º with respect to the spectrometer during measurement. The peaks investigated were the Br 3d, Ge 3d, Ge 2p3/2, C 1s and O 1s. For an exposure of 20 minutes above a 48% HBr solution, we found minimal oxide present. Vapor phase treatment provides a simple method for passivating the sample in a nondestructive and effective manner. Future research will focus on understanding the long-term stability of the passivated surface in air. 1. P. Ponath, A. B. Posadas, and A. A. Demkov, Ge(001) “surface cleaning methods for device integration,” Appl. Phys. Rev. 4, 021308 (2017) 2. K. A. Reinhardt and W. Kern, Handbook of Silicon Wafer Cleaning Technology, Chap. 9. 523-4, 588-589 (1993)Alex_Molina_ERN_Abstract_FINAL.docx
Funder Acknowledgement(s): Funding was provided by the National Science Foundation through the Penn State MRSEC Program DMR-1420620.
Faculty Advisor: Suzanne E. Mohney, firstname.lastname@example.org
Role: I developed and applied the methodology outlined in this abstract. XPS data and analysis was collected and discussed with Jeffrey Shallenberger.