Energy level alignments in strained-layer GaInP/AlGaInP laser diodes: Model solid theory analysis of pressure-photoluminescence experiments

We report high-pressure photoluminescence (PL) experiments on GaInP/AlGaInP laser structures and a comprehensive interpretation of the results via calculations based on the Model Solid Theory (MST) of Van de Walle et al. [1, 2]. This methodology allows an accurate description of the band structure and band offsets in complex heterostructures over a wide range of sample compositions and applied pressures. Measurements are performed on Ga_0.4In_0.6P/(Al_0.6Ga_0.4)_0.5In_0.5P (nominal compositions) double heterojunction samples having active layers of either 125 or 30 Å. Trie pressure data determine a reliable set of deformation potentials for the three constituent binary compounds in this system, InP, AlP and GaP. Using these deformation potentials and a realistic equation of state, the MST calculation gives a reasonable representation of the observed PL spectra over the full presure range (0 to 5 GPa) studied. The conduction band offset ΔE_c, valence band offset ΔE_v, and the bulk bandgap energies are computed in this materials system for a wide variety of conditions. At ambient pressure we find ΔE_c : ΔE_v ≈ 70 : 30, in accord with the consensus value of the band-offset ratio in similar heterostructures. However, our calculations predict band-offset variations with both composition and applied pressure that are non-negligible.