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Long-wavelength vertical-cavity surface-emitting lasers (VCSELs) are desired for low-cost broadband access. Costeffective solutions which are compatible to the widely utilized GaAs technology are desired. High-Speed longwavelength VCSELs, however, require tunnel-junctions (TJs) for low-loss high-speed performance. TJs, on the other hand, are harder to realize on GaAs due to higher bandgaps. Here we report our recent work on highly efficient tunnel junctions grown on GaAs substrates using the InGaAlAsSb material system. We present a detailed analysis both in theory and experiment on several good candidates of low-resistance TJs that may significantly improve the performance of VCSELs and the realization of high performance of long-wavelength VCSELs on GaAs seems feasible. By using high doping p-n junction and hetero junction energy band theory, electrical properties of tunnel junction are calculated. Several tunnel junction structures are analyzed in detail. The influence of doping level on the tunneling current is discussed.
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