Molecular Beam Epitaxial Growth and Characterization of Mismatched InGaAs and InAlAs Layers on InP
Abstract
Mismatched epitaxial layers of In(x)Ga(1-x)As and In(y)Al(1-y)As were grown on (001) InP by molecular beam epitaxy. The layers were characterized by a technique we developed known as variable azimuthal-angle ellipsometry. It reveals large optical anisotropy for many strained layers. We attribute the anisotropy to strain-induced surface roughening during growth. Samples were also characterized by high-resolution x-ray diffraction (HRXRD) to assess layer quality as well as composition and strain. HRXRD measurements reveal orthorhombic distortion of partially relaxed layers of InGaAs and InAlAs in tension or compression, with preferential strain relief in the 110 direction. We show that HRXRD epilayer peak width and interference fringes are sensitive, non-destructive criteria to judge the structural quality of strained heterostructures. For layers ranging from 300 to 10,000 A, with lattice mismatch of +/- 1% or less, the crystalline quality consistently remains high to thicknesses up to 3-9 times the Matthews-Blakeslee critical layer thickness. We investigated the thermal stability of these layers, using HRXRD to measure structural changes caused by high-temperature anneals. We also compared the electron mobility of modulation- doped heterostructures before and after annealing. Both techniques demonstrate that our high-quality strained layers are stable to temperatures of at least 800-859 deg C. We explain this result by the limited sources available for the nucleation of misfit dislocations. The findings are applied to the design and growth of high-performance pseudomorphic InAlAs /InGaAs /InP heterostructure field-effect transistors with layers exceeding the Matthews-Blakeslee limit.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1993
- Accession Number
- ADA342861
Entities
People
- Brian R. Bennett
Organizations
- Massachusetts Institute of Technology