Thickness modulation and strain relaxation in strain-compensated InGaP/InGaP multiple-quantum-well structure grown by metalorganic molecular beam epitaxy on GaAs (100) substrate

• Strain-compensated InGaP/InGaP MQWs were grown by MOMBE on GaAs (100) substrates.
• The TEM image showed noticeable thickness modulation in the barrier layers.
• Analysis of the XRD pattern revealed that large strain relaxation occurred in the well layers.
• Decreasing the substrate temperature suppressed the crystalline degradation.
• The sample grown at 510 °C had 50 times higher PL peak intensity than the sample grown at 530 °C.

We have investigated the structural features of a strain-compensated InGaP/InGaP multiple-quantum-well (MQW) structure on GaAs (100) substrate with a band-gap energy of around 1.7 eV for solar cell applications. In transmission electron microscopy images, noticeable thickness modulation was observed in the barrier layers for a sample grown at the substrate temperature of 530 °C. Meanwhile, the X-ray diffraction patterns indicated that strain relaxation predominantly occurred in the well layers. Decreasing the substrate temperature from 530 to 510 °C was effective in suppressing both the thickness modulation and strain relaxation. Additionally, increasing the growth rate of the well layer further suppressed the thickness modulation. In room-temperature photoluminescence (PL) emission spectra, the sample grown at 510 °C showed approximately 50 times higher PL peak intensity than the one grown at 530 °C.