Excitonic transitions and exciton damping processes in InGaAs/InP

Abstract

Detailed absorption measurements and the analysis of the absorption spectra of In1−x Ga x As lattice matched to InP are reported. The lattice matching parameter Δa/a covered a range from +4×10− 3 to −1×10− 3. From the absorption data of material with small matching parameter we obtain the value of the interband matrix element ( P 2=20.7 eV), the excitonic Rydberg (E x =2.5 meV), and damping constant (Γ0=5.1 meV) in the temperature range from 1.5 to 340 K. From the temperature dependent band‐gap shrinkage and exciton damping constant Γ, information on the carrier‐phonon interaction is obtained. The effect of the biaxial stress in the epitaxial layers caused by the mismatch with the substrate is demonstrated by absorption spectra which directly reveal the valence band splitting due to stress. Absorption measurements on samples with and without substrate indicate that the strained expitaxial layers do not relax completely if the substrate is etched away. The remaining strain field is probably caused by misfit dislocations generated during the epitaxialgrowth. Taking into account these stress effects, a precise value of the band gap as a function of temperature is derived. At zero temperature, we obtain a value of E g (0) =821.5±0.2 meV for the band gap of In0.53Ga0.47As. From the absorption spectra we further determine the value of the bimolecular recombination coefficient (B=0.96×10− 1 0 cm3/s at room temperature). The comparison of material grown by molecular‐beam epitaxy(MBE) and liquid‐phase epitaxy (LPE) shows that there is no difference between significant optical data of LPE and MBE high‐quality layers.