Characterization of ErAs-GaAs Epitaxial Layers from NIST.

摘要

A key aspect of our project is obtaining new ErAs:GaAs epitaxial layers for the development of useful THz extrinsic-photoconductive (PC) devices. To accomplish this a CRADA and purchase order were established with Dr. Rich Mirin at NIST in Boulder, CO. Dr. Mirin did his Ph.D. in the same molecular-beam epitaxy (MBE) group at UC Santa Barbara that developed the useful ErAs:GaAs epitaxial layers in the late 1990s. During the reporting period, Dr. Mirin delivered to Dr. Brown s group at Wright State four ErAs:GaAs epitaxial layers on 3-inch SI-GaAs substrates. The first two were morphologically rough and not amenable to optical testing. The second two were much better and are described in the associated Technical Report. Wright State carried out three important characterizations of these two samples: (1) sheet resistance measurements by the four-point-probe method, (2) VIS-IR measurements of the transmittance around the GaAs band-gap, and (3) ultrafast pump-probe phototransmission measurements with a 1550-nm (EDFA) mode-locked laser. All three provided interesting results, especially the ultrafast pump-probe characterizations which demonstrated approximately 0.33 ps FWHM for each of the two promising samples. The near-term plan is to start fabricating PC switches and photomixers with these samples during October 2013 in the new WSU cleanroom.