Measurement of the direct energy gap of ${\mathrm{Al}}_{0.5}$${\mathrm{In}}_{0.5}$P: Implications for the band discontinuity at ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$P/${\mathrm{Al}}_{\mathit{y}}$${\mathrm{In}}_{1\mathrm{-}\mathit{y}}$P heterojunctions

In a recent paper [Phys. Rev. B 48, 18 031 (1993)], Patel and co-workers described hydrostatic-pressure-dependent photoluminescence measurements performed on ${\mathrm{Ga}}_{0.47}$ ${\mathrm{In}}_{0.53}$P/${\mathrm{Al}}_{0.5}$ ${\mathrm{In}}_{0.5}$P multiple quantum wells. They determined directly a valence-band offset of 0.24±0.05 eV from the energy difference between the indirect transition in the barrier and the transition from X states in the barrier to hh1 valence-band states in the quantum well, when extrapolated to zero pressure. The conduction-band offset was then indirectly determined to be 0.26 eV from the total-band discontinuity of the system, assuming a value of 2.45 eV for the (low temperature) lowest-energy direct gap of ${\mathrm{Al}}_{0.5}$ ${\mathrm{In}}_{0.5}$P. This yields a band-offset ratio, Δ${\mathit{E}}_{\mathit{c}}$:Δ${\mathit{E}}_{\mathit{v}}$, of 52:48. Here, we present evidence that the (5 K) direct gap of the ${\mathrm{Al}}_{0.5}$ ${\mathrm{In}}_{0.5}$P barrier is ∼2.685 eV, which results in a revised band-offset ratio of 67:33, similar to recent values determined for ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{In}}_{\mathit{x}}$P/(${\mathrm{Al}}_{\mathit{y}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{y}}$ ${)}_{0.5}$ ${\mathrm{In}}_{0.5}$P heterojunctions.