Defect density measurements of low temperature grown molecular beam epitaxial GaAs by photothermal deflection spectroscopy <AUTHGRP>

The subgap optical absorption of GaAs layers grown by low temperature molecular beam epitaxy is measured by photothermal deflection spectroscopy (PDS). The absorption increases as the growth temperature decreases at a fixed wavelength. Defect densities evaluated from the absorption spectra and the known absorption cross sections are between 10¹⁸and10¹⁹cm ^-3. It is shown that complementary PDS phase spectra can be used to separate the absorption of the epitaxial layers from the bulk.