Electrical and structural properties of dislocations confined in a InGaAs/GaAs heterostructure

Abstract

Electrical activation and structural defects in lattice-mismatched InGaAs/GaAs heterostructures are studied using the capacitance-voltage method, deep-level transient spectroscopy, and cross-sectional transmission electron microscopy. Confinement of structural defects is observed in an In0.2Ga0.8As/GaAs heterostructure with a relaxed InGaAs layer thicker than the thickness of the critical layer. When In composition is 0.2, where the lattice mismatch is 1.4% between InGaAs and GaAs, a two-dimensional growth mode dominates. Misfit dislocations are formed and conduction electrons are depleted only near the InGaAs/GaAs interface. Carrier depletion is related to an electron trap with an activation energy of 0.395 eV and a capture cross section of 1×10−16 cm2 induced by deformation. Electrical evaluations show that electrical activity in the InGaAs layer does not degrade by interfacial dislocations. Therefore, a good-quality InGaAs layer is provided though the thin layer near the interface is of poor quality. These results indicate that elastic strain is not large enough in this system for dislocations to rise to the surface. In an In0.4Ga0.6As/In0.2Ga0.8As/GaAs heterostructure, however, dislocation confinement is imperfect in spite of similar lattice mismatches between each of the interfaces. In this structure, threading dislocations rise into the epitaxial layer not only from the In0.4Ga0.6As/In0.2Ga0.8As interface but also from the In0.2Ga0.8As/GaAs interface. This indicates that dislocations can be generated in the layer that had already been formed during the growth of an upper layer.

Deep levels caused by misfit dislocations in GaAsSb/GaAs heterostructures

“…Although this level is 0.1 eV shallower than the ED1 level in GaAs, it is believed that they both have the same origin and the difference in their level positions with respect to the conduction-band edge results from the band-gap narrowing in the ternary compound. Later on, Uchida et al 6 found by DLTS a deep level associated with misfit dislocations in InGaAs/GaAs heterostructures with a 20% In content, grown by molecular beam epitaxy. This level is probably of the same origin as ED1.…”

“…4 versus the band-gap energy of the respective compound. In addition, the results for In x Ga 1Ϫx As layers with xϭ6% and xϭ20% obtained previously 5,6 are included in the figure. The observed dependence points out that the energy level position of the trap with respect to the top of the valence band remains constant in each material, suggesting that the defect state is composed primarily of the valence band states.…”

Distinction investigation of InGaAs photodetectors cutoff at 2.9μm

“…It can be seen that at the same doping temperature sample A shows lower carrier concentration in the InGaAs absorption layer. One possible reason is due to the carrier depletion cause by the electrical inactivation of dopant and electron trap, for example, formed by misfit dislocations [16].…”

Electrical characterization of partially relaxed InxGa1−xAs/GaAs multiple quantum well structures

“…[3][4][5][6] So far most of the studies on the electrical properties of the strain-relaxed InGaAs/GaAs system have been concerned with single or double heterostructures. 7,8 The strain relaxation in MQWs or superlattices has been mostly studied by using x-ray diffraction, transmission electron microscopy, and photoluminescence techniques. 4,5,9,10 In this letter, we report on the electrical properties of partially relaxed In x Ga 1Ϫx As/GaAs MQW structures.…”