GROWTH AND CHARACTERIZATION OF COMPOSITIONALLY GRADED, RELAXED SI1-XGEX

Compositionally graded, relaxed, n-type, Si1-xGex alloy layers have been grown on (100) Si substrates; the main emphasis has been put on compositions with x = 0.25. It is found that for substrate growth-temperatures higher than similar to 750 degrees C and a grading rate of 10% Ge/mu M relaxed Si0.75Ge0.25 epitaxial layers of high structural, optical and electrical quality can be grown. The layers are characterized by channeling parameters close to expected bulk values, a threading dislocation density of similar to 5 x 10(5) cm(-2), and strong near-band gap luminescence. Electrical measurements have revealed Hall mobilities similar to published bulk values and concentrations of electrically active deep levels less than or equal to 2 x 10(11)cm(-3). The surface morphology is, however, strongly influenced by the grading procedure which produces a high degree of cross-hatching.