L-band recombination in ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$P/${\mathrm{In}}_{0.5}$${\mathrm{Al}}_{0.5}$P multiple quantum wells

We report the direct observation of recombination from the ${\mathit{L}}_{1\mathit{c}}$ band in ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$P/${\mathrm{In}}_{0.5}$${\mathrm{Al}}_{0.5}$P multiple quantum wells. The indirect ${\mathit{L}}_{1\mathit{c}}$ transition is observed in unstrained structures with narrow wells and in tensile strained structures, using high-pressure photoluminescence measurements. ${\mathit{L}}_{1\mathit{c}}$ recombination is characterized by a pressure coefficient of 60± 5 meV/GPa, considerably smaller than that of the direct gap ${\mathrm{\Gamma }}_{1\mathit{c}}$ states. In the same experiments we also identify heterostructure states associated with ${\mathrm{\Gamma }}_{1\mathit{c}}$ and ${\mathit{X}}_{1\mathit{c}}$ from which we determine the separation among the conduction minima in unstrained bulk ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$P for x≤0.48. © 1996 The American Physical Society.