Metalorganic vapor phase growth of quantum well structures on thick metamorphic buffer layers grown by hydride vapor phase epitaxy

Abstract

The hydride vapor phase epitaxy technique (HVPE) can deposit uniform materials at high growth rates, making it suitable for the formation of metamorphic buffer layers (MBLs). HVPE was used to form InxGa1−x As-based MBLs as substrates in the metalorganic vapor phase epitaxy (MOVPE) of superlattice (SL) structures. Samples were grown over a range of deposition temperatures and reactant flows and their effect on the ternary alloy composition and growth rate was determined. Over the compositional range of xInAs<0.4, the alloy composition varied almost linearly with indium chloride pressure (PInCl). A compositionally step-graded MBL consisting of nine intermediate steps followed by a thick, constant composition layer of xInAs∼0.23 was grown. The MBL was characterized by high-resolution x-ray diffraction (HRXRD) and reciprocal space mapping. The topmost layer was highly relaxed, exhibiting a residual strain of −0.0011±0.0002. Chemical-mechanical polishing (CMP) was used to reduce the surface cross hatching, affecting a decrease in rms roughness from 2.10 to 1.39nm. A 20 period, In0.33Ga0.67As (3.1nm)/Al0.90In0.10As (7.2nm) strain-balanced superlattice (SL) structure was grown by MOVPE on the as-grown and CMP-prepared MBL and characterized by HRXRD. The diffraction pattern of the SL grown on the CMP-prepared MBL was significantly more intense with narrower x-ray diffraction peaks when compared with the SL on as-grown MBL.