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Previous Research : Antimonides - Transport and Optics |
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Introduction:We have run a long standing program on the properties of quantum wells, heterojunctions and superlattices made using antimonide based materials. This involved the development of the growth of these structures by MOVPE. We have a large back catalogue of interesting structures which are still used for some research on quantum transport and optics. In general, the use of antimony based compounds leads to narrower gaps and type II (broken gap) behaviour due to the large valence band discontinuity associated with antimony/arsenic interfaces. These structures exhibit interesting electrical and optical properties often associated with the simultaneous existence of electrons and holes in the structures.  Electrical properties:Two-Dimensional (2D) systems based on GaSb (for example (Ga,In)Sb quantum wells) allow the investigation of 2D hole gases. Structures based on InAs/(Ga,In)Sb allow the particularly interesting study of complex bipolar transport involving both 2D electrons and 2D holes. This has led to the discovery of the Zero Hall Resistance state. The crossed electron and hole band dispersion relations form a miniband gap where they cross which causes negative magnetoresistance and can also be observed optically in the far infrared. We have developed a gating technology to allow us to tune the Fermi level through the miniband gap. Optical PropertiesInAs/(Ga,In)Sb superlattices are the basis of 5-10um detectors using III-V semiconductors. InSb, In(As,Sb) and InAs/In(As,Sb) superlattices are further candidates in this region of the infra-red spectrum. The 1.75um band gap of GaSb could lead to structures based on GaSb with applications in the 1.2-1.7um region with is associated with fibre optic devices. GaSb/(Ga,In)Sb structures can extend this range to about 3um. Non-linear absorption is studied using the FELIX high intensity free electron laser. |
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