  We experimentally investigate and analyze the electrical and optical
characteristics of GaAs-based conventional quantum well laser diodes and the
quantum well laser diodes with slightly-doped tunnel junction. It was found
that TJ LD show a nonlinear S-shape I-V characteristic.It was also found that
the internal quantum efficiency measured by 21% and 87.3% for the TJ LD and the
conventional LD, respectively. Furthermore, compared with the conventional LD,
it was found that we could achieve 15 nm broadband spectrum from the TJ LD due
to lasing dynamics reflects the current dynamics. The results may also lead to
the realization of more applications.
