What property of an LED's semiconductor material determines its forward voltage drop?

A Light Emitting Diode (LED) operates by electrons recombining with holes across the semiconductor's depletion region, releasing energy in the form of a photon. The amount of energy required for this crossing, and subsequently the color of the emitted light, is determined by the material's 'band gap.' Because the band gap dictates the energy difference between the valence and conduction bands, it directly controls the forward voltage drop required to push current through the diode. Materials with larger band gaps produce higher energy light (like blue or ultraviolet) and therefore exhibit a higher forward voltage drop. Distractors like intrinsic resistance or junction capacitance affect other operational parameters but do not define the baseline voltage drop necessary for light emission. The fundamental property dictating both the voltage requirement and the photon wavelength is the band gap.