QUANTUM WIRE ARRAYS INVESTIGATED BY MEANS OF HIGH-RESOLUTION X-RAY DIFFRACTION. L. Tapfer, L. De Caro, C. Giannini, and Y. Zhuang, Centro Nazionale Ricerca e Sviluppo Materiali (PA.S.T.I.S.-C.N.R.S.M.), S.S.7 Appia Km. 712,1-72100 Brindisi, Ita1y

The geometrical and structural properties of periodic surface structures such as surface gratings, quantum wire and quantum dot arrays are investigated by high-resolution double-crystal and triple-crystal x-ray diffraction, reciprocal space mapping and x-ray reflectivity. The periodic surface structures are fabricated on (100)GaAs surfaces and MBE-grown AlGaAs/GaAs and InAs/GaAs multiple quantum well heterostructures by holographic lithography and subsequent dry-etching.

The analyses of the experimental x-ray diffraction patterns are performed by using a semi-kinematical scattering model. Simulations of the diffraction patterns and the reciprocal space maps allow us to determine the shape of the corrugation and geometrical parameters of the wires and dots. The x-ray data are compared with the results obtained by electron microscopy.

Diffraction patterns recorded in symmetrical and asymmetrical scattering geometries reveal a partial elastic lattice relaxation of the heterostructures which is caused by the finite lateral size of the quantum wires. It is shown that the tetragonal unit cells of the multiple quantum well wire structures are orthorhombically distorted due to the partial relaxation. An elasticity model which takes into account the lattice coherence at the wire/substrate interface along the wire direction explains and describes the data obtained from the x-ray diffraction experiments quantitatively.