Magnetic-field-induced free electron and hole recombination in semimetallic ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$Sb/InAs quantum wells

We observed the carrier-concentration dependence of the magnetic-field-induced free electron and hole recombination in semimetallic ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$Sb/InAs quantum wells. The electrons and holes recombined when the highest-hole Landau level crossed the Fermi level. The recombination continued with increasing field until all the holes vanished, leading to a semimetal-to-semiconductor transition. This transition shifted to a higher field when the electron concentration decreased.