X-ray Study of Interdiffusion and Strain Relaxation in Annealed (SimGen)p Atomic Layer Superlattices

Abstract

ABSTRACTWe have studied interdiffusion and strain relaxation induced by annealing in (SimGen)p atomic layer superlattices grown by MBE using x-ray diffraction techniques. In these expertments, an interdiffusion coefficient Dλ. was determined by monitoring as a function of time, for annealing temperatures between 550° C and 700° C, the decay of the low angle first order 000 diffraction peak arising from the composition modulation wavelength ° of the superlattice. Strain relaxation was studied by measuring the angular shift of the superlattice 400 reflection on annealing. The strain was found to decrease exponentially and although most of the relaxation occurred within the first few minutes of annealing, residual strain was detected after several hours of heat treatment. During relaxation the low angle reflection peak intensity exhibited a rapid decay corresponding to an interdiffusion coefficient Dλ of the order of 5 × 10−23 m2s−1 at 700° C on structures grown on (100) Si with λ ≅ 1.5 nm. After most of the strain has been relieved, a slower linear decay rate was observed indicating a significant decrease of Dλ. The variation of Dλ with periodicity was explored and interdiffusion for structures grown on (100) Si and on Sil-xGex (0<x<l) buffers was compared.