Real-time assessment of In surface segregation during the MBE growth of AlSb/InAs(Sb) heterostructures

It is now well established that In surface segregation prevents the formation of abrupt interfaces for In containing III-V heterostructures. Despite the drastic effects of In surface segregation on the actual potential profiles at quantum-well interfaces, only scarce results are available for the InAs/(Al,Ga)Sb material system. However, this material system has recently gained much technological interest, in particular because it is well suited for the achievement of room-temperature quantum-well laser diodes emitting in the 3-5 /spl mu/m mid-infrared spectral domain. The purpose of this communication is to show that In surface segregation can be evidenced in real-time during the growth of AlSb on InAs(Sb) by MBE using reflection high-energy electron diffraction (RHEED). The. interface width deduced from RHEED measurements (five monolayers (/spl plusmn/1 ML) for example at a standard growth temperature of 430/spl deg/C) agrees very well with the one observed by high-resolution transmission electron microscopy. Moreover, the influence of growth parameters on the In segregation length (/spl omega/) at the AlSb on InAs(Sb) interface and on the associated segregation ratio R = e/sup -1//spl omega// can easily be evaluated from RHEED measurements. The In segregation length (/spl omega/) is found to increase with the growth temperature (from /spl ap/5 to 15 ML in the 430-520/spl deg/C temperature range) as expected for a kinetically limited surface segregation phenomenon. The associated segregation ratio R varies from 0.8 to 0.9. These results indicate that the composition and therefore the band profile of InAs/AlSb heterostructures are strongly affected by indium surface segregation at AlSb on InAs interfaces.