Influence of substrate misorientation on the structural characteristics ofInGaAs GaAs MQW on (111)B GaAs grown by MBE

The dependence of the defect structure on substrate misorientation is inves tigated in InGaAs/GaAs(111) multiple quantum well heterostructures. Samples were simultaneously grown by molecular beam epitaxy on GaAs(111)B substrat es misoriented 1 degrees off towards [(2) over bar 11] and 2 degrees off to wards [2 (1) over bar (1) over bar] under optimized growth conditions for b oth off-axis substrates, For both substrate misorientations two different d islocation networks are evidenced: first, a triangular 60 degrees misfit di slocation array with [(1) over bar (1) over bar (1) over bar] directions an d second, a new dislocation configuration seen for the first time with disl ocation lines parallels to [11 (2) over bar] directions. This latter can wo rk as a dislocation multiplication source for In-content above 25% for the structure chosen being more active in 2 degrees off substrates than in 1 de grees off ones. The activation of this new dislocation source may drastical ly affect the optical properties of the multiple quantum wells. (C) 1999 El sevier Science S.A. All rights reserved.