AVS 52nd International Symposium
    Electronic Materials and Processing Tuesday Sessions
       Session EM-TuP

Paper EM-TuP20
Contact Properties in Metal/Molecule/GaAs Devices

Tuesday, November 1, 2005, 4:00 pm, Room Exhibit Hall C&D

Session: Electronic Materials and Processing Poster Session
Presenter: P.D. Carpenter, Purdue University
Authors: P.D. Carpenter, Purdue University
S. Lodha, Purdue University
Q. Hang, Purdue University
D.B. Janes, Purdue University
Correspondent: Click to Email
Molecular devices have typically been fabricated in a metal/molecule/metal configuration.@footnote 1@ However, the use of semiconductor contacts in molecular devices allows for control in device performance by varying the doping density and the surface properties of the semiconductor substrates. Semiconductors, such as GaAs, also allow for stable bonds to molecular layers. In this work, molecular devices have been fabricated in a metal/molecule/GaAs device structure using standard photolithography techniques and solution-based growth of self-assembled monolayers (SAMs).@footnote 2@ After SAMs were formed on the GaAs surface, a top metal contact was formed using an indirect path, low energy evaporation technique. The effect of the doping density (n-type and p-type) and surface properties of the substrates, including surface layers incorporating defect states, have been studied in devices employing both aromatic and alkanethiol SAMs. An electrostatic model was developed to calculate the energy band diagrams of the structures and to explain the current-voltage results. Upon examination of the I-V characteristics of the devices, we see an increase in conductivity from the fabricated metal/semiconductor control devices. It has been shown that the electrical performance of the device can be modulated by changing the coupling of the molecular monolayer with the top contact metal and the GaAs substrate. This coupling can be changed by varying the work-function of the metal contact, or by changing the doping type in the GaAs or by incorporating defect states near the GaAs surface.@footnote 3@ Alternate metallization techniques, including shadow masking approaches to avoid process-related damage to the SAM, have also been developed. @FootnoteText@ @footnote 1@ M. Reed, et. al., Science, vol. 278, pp. 252-254 (1997).@footnote 2@ S. Lodha and D. B. Janes, et al., Appl. Phys. Lett., vol. 85, 2809 (2004).@footnote 3@ S. Lodha, P. D. Carpenter, and D. B. Janes, unpublished.