Growth and characterization of GaAs on sapphire (0001) by molecular beam epitaxy

Abstract

Crystal epilayers of (lll)-oriented GaAs have been grown successfully on sapphire (Oool) substrates by molecular beam epitaxy. Although the epilayers were found to have a very high twin density, large areas (cm2) with no grain boundaries were observed. Both substrate surface preparation and temperature controlled the crystallinity. Reflection high-energy electron diffraction (RHEED) was used to characterize the sapphire surface after omne cleaning.RHEED patterns taken at several azimuths were consistent with an outermost layer of oxygen atoms. Powder x-ray diffraction and rotation x-ray photographs were used to determine growth conditions that resulted in an improvement in the crystalline order. Cross-sectional transmission electron microscopy confirmed the crystalline nature of the GaAs epilayers. The quality of the CaAs was also characterized by photoluminesceace. Finally, crystalk quality was Bssessed using double-crystal x-ray diffraction rocking curves.

Improving the Material Quality of GaAs Grown on the c-Plane Sapphire by Molecular Beam Epitaxy to Achieve Room-Temperature Photoluminescence

“…At the LT growth, two peaks are observed at 1.518 and 1.49 eV. The high-energy peak is related to the free exciton (FE) emission, while the low energy peak is attributed to free or donor-bound electron-to-acceptor recombination. , The FE peaks of the other two samples are shifted a few meV due to the local stress in the GaAs lattice caused by impurities in it …”

“…9,37 The FE peaks of the other two samples are shifted a few meV due to the local stress in the GaAs lattice caused by impurities in it. 9 We have investigated the RT-PL for all samples. Apart from the sample grown at 650 °C (S6), we were unable to get a detectable PL signal from the remaining samples, which is consistent with the better RC width of sample S6.…”

“…The high lattice mismatch (∼46%) and dissimilarity in crystal structures (zinc blende GaAs, trigonal sapphire) introduce threading dislocations, misfit dislocations, and stacking faults in the film. These will ultimately lead to poor surface morphology as well as deteriorated electrical and optical properties of the grown materials. ,− Considering these challenges, a comprehensive growth study must be done to understand the effect of different growth parameters on the structural and optical properties of GaAs.…”