Reduction of hetero-interface resistivity in n-type AlAsSb/GaSb distributed Bragg reflectors

Graded interface layers are commonly known to reduce the electrical series resistance of distributed Bragg-reflectors in vertical-cavity surface-emitting lasers in various material systems such as AlAs/GaAs or AlInAs/GaInAs. As these materials can be highly n-doped using silicon, a further decrease of the resistivity is easily achieved. However, for n-type GaSb/AlAsSb distributed Bragg reflectors on GaSb-substrates the free electron density due to doping in graded layers is reduced depending on the aluminum content and therefore optimized structures are hard to design. In this paper, we present electrical measurements on various grading and doping schemes, yielding a low-resistive interface suitable for application in mid-infrared vertical-cavity surface-emitting lasers.