Strain evolution and confinement effect in InAs/AlAs short-period superlattices studied by Raman spectroscopy

Raman spectra of two series of InAs/AlAs short-period superlattices were measured at room temperature to investigate the impact of strain on the phonon modes taking into consideration the confinement effect and interface mode. The evolution of strain in the InAs layer and the AlAs layer was studied in (InAs)(2)/(AlAs)(2) superlattices grown at various temperatures (400-550 degrees C). While the strain existed in the AlAs layer remained almost constant, the strain in the InAs layer varied significantly as the growth temperature increased from 500 to 550 degrees C. The confinement effect on the optical phonons was analyzed based on results from (InAs)(n)/(AlAs)(n) grown at 450 degrees C (n = 2, 3, 4, and 5). Additionally, the confinement effect was found to be stronger in shorter periods with higher interface quality. The interface phonon modes were resolved between the longitudinal optical and transverse optical phonon modes, which assist in the rough estimation of the thickness of the layers. The disorder-activated acoustic phonon modes at the low-frequency side were also addressed.

Automated summary

Raman spectra were used to study the strain's effect on phonon modes in InAs/AlAs short-period superlattices, considering confinement effect and interface mode. The strain in the InAs layer varied significantly at different growth temperatures while strain in the AlAs layer remained constant. Confinement effect was found to be stronger in shorter periods and higher interface quality superlattices, affecting optical phonons. Interface phonon modes were resolved for thickness estimation, and disorder-activated acoustic phonon modes were discussed.