CURRENT SPREADING IN PROTON-IMPLANTED VERTICAL-CAVITY TOP-SURFACE-EMITTING

In the paper, the current spreading phenomenon is analysed in proton-i mplanted vertical-cavity top-surface-emitting lasers (VCSELs). A simpl e approximation analytical relation was derived for a radial distribut ion of the current density entering the active regions of these lasers . This distribution is nearly uniform in the case VCSELs with a very s mall active region of radius R(A) less than or similar to 2 mu m but b ecomes more and more non-uniform with an increase in the active region 's size. In VCSELs with very large active regions (r(A) greater than o r similar to 10 mu m), most current flows within a narrow annular area close to the active-region perimeter. This non-uniformity should be t aken into account in modelling all physical phenomena in VCSEL structu res that are influenced by distributions of a current density or a car rier concentration within their active regions.