Reduced Dislocation Density of an InP/GaAs Virtual Substrate Grown by Metalorganic Chemical Vapor Deposition

• Published in: Coatings (Basel) Vol. 12; no. 6; p. 723
• Main Authors: Tsai, Yu-Li, Wu, Chih-Hung
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.06.2022
• Subjects: Analysis; Annealing; Buffers; Chemical vapor deposition; Computational grids; Dislocation density; Dislocation mobility; Epitaxial growth; Epitaxy; Gallium arsenide; Indium; Indium gallium arsenides; Indium phosphides; Intermetallic compounds; Lattice parameters; Low temperature; Metalorganic chemical vapor deposition; Methods; Microscopy; Misfit dislocations; Nucleation; Optoelectronic devices; Photoluminescence; Room temperature; Structural analysis; Substrates; Thermal expansion; Threading dislocations; Taiwan; United States > US
• ISSN: 2079-6412; 2079-6412
• DOI: 10.3390/coatings12060723

Integrating indium phosphide (InP) material on a gallium arsenide (GaAs) substrate to form an InP/GaAs virtual substrate has been an attractive research subject over the past decade. However, the epitaxial growth of InP on GaAs is challenging due to a large mismatch in the lattice constant and thermal expansion coefficient. This paper describes the successful hetero-epitaxy of InP on a GaAs substrate by metalorganic chemical vapor deposition. The hetero-epitaxy in this study utilized a hybrid growth method involving a thin indium gallium arsenide (InGaAs) linearly graded buffer, two-step InP growth, and a post-annealing process. Transmission electron microscopic observations showed that a traditional two-step InP/GaAs virtual substrate was smooth but had a high threading dislocation density (TDD) of 1.5 × 109 cm−2 near the InP surface. The high TDD value can be reduced to 2.3 × 108 cm−2 by growing the two-step InP on a thin InGaAs linearly graded buffer. The TDD of an InP/GaAs virtual substrate can be further improved to the value of 1.5 × 107 cm−2 by removing the low-temperature InP nucleation layer and carrying out a post-annealing process. A possible reason for the improvement in TDD may relate to a dislocation interaction such as the annihilation of mobile threading dislocations. Room-temperature photoluminescence spectra of InP/GaAs virtual substrates with different TDD values were compared in this study. The optical and micro-structural characterization results suggest that the proposed growth method may be feasible for making good-quality and relatively low-cost InP/GaAs virtual substrates for the integration of optoelectronic devices on them.