Growth of AlGaAs and GaAs by atmospheric-pressure MOCVD on lenticular substrates

Abstract

Critical orientation effects are well known in epitaxial layers grown by VPE and LPE. More recently, effects have been observed in rough growth in MBE-grown AlGaAs and as faceted morphology and terraces in MOCVD-grown AlGaAs and GaAs. For the case of growth by LPE and MBE, a critical misorientation unique to the growth conditions resulted in a smoothening of rough or terraced growth morphology. In addition, MBE-grown AlGaAs deposited on lens-shaped substrates at growth temperatures below 700 °C resulted in atomically smooth morphology and improved photoluminescence (PL) spectra for substrate areas having a critical misorientation toward the nearby (111)A planes, whereas the epitaxial films grown elsewhere (including the nominally (100)-oriented center of the substrate) were rough and had poor quality PL. This work describes a study of the growth by atmospheric-pressure MOCVD at 650–700 °C of AlGaAs and GaAs on lens-shaped substrates which sample surface misorientations up to 22° from the (100). Only visually smooth growth and no change in the band-edge PL wavelength were observed for small misorientations from the (100) plane under these growth conditions, in contrast to readily observed rough morphology patterns and PL band-edge shifts in MBE. Patterns of rough growth due to microscopic point defects associated with specific crystalline orientations were observed for both MOCVD-grown AlGaAs and GaAs films for surface misorientations greater than 10°.