Imperfections in vapor-phase epitaxial GaAs revealed by Sirtle etchant

The authors apply their studies of recombination, electrophysical, and structural properties of epitaxial films to determine the nature of imperfections revealed in gallium arsenide when it is treated with Sirtle etchant. They studied n-type epitaxial layers grown in the (100) orientation by vapor-phase epitaxy on heavily Te-doped and semiinsulating gallium arsenide substrates. With the aim of obtaining information on the nature of the defects, they carried out scanning electron microscopy using secondary emission; induced current and cathode luminescence techniques; transmission electron microscopy in the transmission regime; selective chemical etching combined with optical microscopy; and the measurement of basic electrophysical parameters of the epitaxial films. Imperfections revealed by Sirtle etchant as domelike etch figures are accumulations of impurity defects in thin layers of epitaxial films. These inhomogeneities may form because of impurity atoms gettering at the drains and may lower the concentration of inactive polluting impurities. They have shown that the observed imperfections are electrically active and make up regions of nonradiative recombination.