Deep levels and a possible d-x-like center in molecular beam epitaxial inxal1−xas

The work reported here was performed in order to establish whether or not complex defects like the D-X center can be present in InAlAs. Dominant deep electron and hole traps in lattice-matched In_0.52Al_0.48As/InP have been identified and characterized. The traps have activation energies ranging from 0.25 to 0.95 eV. The electron traps have very large capture cross-sections,~10⁻¹²-10⁻¹¹ cm², similar to attractive centers. The lattice-matched samples do not show any persistent photoconductivity effects at low temperatures. In strained In_1−xAl_xAs with 0.48 <x ≤ 0.57, an electron trap with a thermal ionization energy of 0.35 eV, a strong dependence of its concentration on donor doping and very small thermal capture cross-section, 10¹⁸ cm², is identified. These samples exhibit persistent photoconductivity. We believe this trap is similar to the D-X center commonly observed in Al_xGa_1−xAs forx ≥ 0.28. He was on leave with the Solid State Electronics Laboratory, Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, MI 48109. He is with the Institute of Radio Physics and Electronics, The University of Calcutta, Calcutta, India 700 009.