Why is a laser diode heavily doped?

A laser diode is heavily doped to provide more electrons and holes for the recombination process that generates light. This heavy doping creates a high carrier concentration, which is essential for achieving the population inversion necessary for stimulated emission. The presence of a sufficient number of electrons and holes in the active region of the diode improves the efficiency of light production, allowing for a more intense output.

In the context of laser operation, the key principle is that when electrons from the conduction band recombine with holes in the valence band, they release energy in the form of photons—the light we see emitted by the laser. The heavy doping ensures that there are ample carriers available for this recombination process, thus enhancing the overall performance of the laser diode.

While factors such as thermal conductivity, band gap energy, and forward bias voltage are indeed important to consider in the operation of semiconductor devices, they are not the primary reasons for heavy doping in laser diodes. The focus on increasing carrier density through heavy doping directly correlates with the mechanism of light generation, which makes this the correct reason in the context of the question.