Growth of strained-layer GaAs/Ge superlattices by magnetron sputtering: Optical and structural characterization (original) (raw)

Epitaxial Growth of Strained Ge Films on GaAs(001)

Thin Solid Films, 1999

Ge films were grown epitaxially as well as pseudomorphically on GaAs(001) substrates at different temperatures using high-vacuum magnetron sputtering. The crystal quality of the resultant layers was examined by high-resolution X-ray diffraction (HRXRD). The rocking curves of Ge layer grown at temperatures greater than 470°C show clear Pendellösung oscillations, confirming the high crystalline quality of the Ge layers. The angular

X-ray investigation of thick epitaxial GaAs/InGaAs layers on Ge pseudosubstrates

2005

We present an investigation of a series of samples with GaAs/InGaAs layers grown on Ge/Si pseudo-substrates. The strain in the GaAs and InGaAs layers were calculated after measuring the lattice constants of the layers using the X-ray diffraction technique. Both layers were found to be under low tensile stress resulting from the lattice mismatch and the difference in thermal expansion coefficients between the adjacent layers. We explore a new concept based on counterbalancing this thermal stress.

Electronic structure of Ge/Si monolayer strained-layer superlattices

Physical Review B, 1989

We report the results of a study of Ge/Si strained-layer superlattices grown on (001) Si substrates. These results allow us to study the transition between superlattice and bulk states. We have exam-0 ined samples whose superlattice period lies between 3 and 15 A, similar to the lattice parameter of the crystalline unit cell. All of the samples in this study are ordered superlattices with an average composition of Geo, Sio,. Intentional ordering on a monolayer scale was achieved by molecularbeam epitaxy. The optical energy-level spectra of these structures at critical points in the Brillouin zone were measured by Schottky-barrier electroreflectance in the energy range 0.6 to 4 eV. Some features of these spectra can be attributed to the creation of new band-to-band optical transitions that are induced by the artificial periodicity imposed on the sample during growth. These new energy levels are derived from bulk Si and Ge energy levels modified by heterojunction offset, strain, and the lower symmetry of the new unit cell. Several of the new optical transitions observed between 0.6 and 1.5 eV are normally forbidden or weakly allowed. The observation of relatively strong transition amplitudes in electroreflectance suggests that electric field effects and deviations from an ideal diamond-lattice structure may play an important role in the enchancement of transition probabilities in superlattice structures.

Si/Ge - Heterostructures - Stability of Strained Layer Superlattices

Solid State Phenomena, 1991

The diamond lattice type group IV semiconductors C, Sic, Si and Ge exhibit an indirect band gap with the conduction band minimum outside the Brillouin zone center. Ultrathin superlattices are predicted to convert the indirect band gap into a quasi-direct one under certain circumstances. Growth of Si/Ge strained monolayer superlattices (SMS) by molecular beam epitaxy is explained, and experimental results obtained with these strucures are discussed.

Critical thickness of Ge/GaAs (001) epitaxial films

Epitaxial single crystal films of Ge, with thickness from 0.2 to 2.4 µm, were grown on GaAs (001) by rf sputtering. These layers were characterized by High Resolution X-Ray Diffraction (HRXRD). Measured rocking curves show that pseudomorphic samples with good structural quality can be obtained by this growth technique. Asymmetrical reflections (115) and (-1-15) are used to determine the in-plane and in-growth lattice parameters of the grown films. From the behavior of these parameters and Ge diffraction peak broadening, with the layer thickness, an experimental value of 1.8 µm is obtained for the critical thickness of Ge grown on GaAs (001).