Until now, micrometer-scale or larger crystals of the III-V semiconductors have not been grown at low temperatures for lack of suitable crystallization mechanisms for highly covalent nonmolecular solids. A solution-liquid-solid mechanism for the growth of InP, InAs, and GaAs is described that uses simple, low-temperature (≤203°C), solution-phase reactions. The materials are produced as polycrystalline fibers or near-single-crystal whiskers having widths of 10 to 150 nanometers and lengths of up to several micrometers. This mechanism shows that processes analogous to vapor-liquid-solid growth can operate at low temperatures; similar synthesis routes for other covalent solids may be possible.

https://science.sciencemag.org/content/sci/270/5243/1791.full.pdf

Solution-Liquid-Solid Growth of Crystalline III-V Semiconductors: An Analogy to Vapor-Liquid-Solid Growth

Data are presented on the conversion (selective conversion) of high‐composition (AlAs)x(GaAs)1−x layers, e.g., in AlxGa1−xAs‐AlAs‐GaAs quantum well heterostructures and superlattices (SLs), into dense transparent native oxide by reaction with H2O vapor (N2 carrier gas) at elevated temperatures (400 °C). Hydrolyzation oxidation of a fine‐scale AlAs(LB)‐GaAs(Lz) SL (LB +Lz≲100 A), or random alloy AlxGa1−xAs (x≳0.7), is observed to proceed more slowly and uniformly than a coarse‐scale ‘‘alloy’’ such as an AlAs‐GaAs superlattice with LB + Lz≳200 A.

Hydrolyzation oxidation of AlxGa1−xAs‐AlAs‐GaAs quantum well heterostructures and superlattices

Because the electroabsorption effect in semiconductor multiple quantum well material is approximately 50 times larger than in bulk semiconductors, significant interest has been generated in the use of MQW's in optical modulators Small high-speed devices have been made which show promise for external modulators in optical transmission systems, as well as for encoding and processing components in optical interconnect and signal processing systems The fact that these modulators are made from III-V semiconductors had led to interest in integration of these components with other active optoelectronic components Although most devices have operated with light of a wavelength of 085 mu m, recently much progress has been made in applying this technology to devices operating near 155 mu m The author reviews the work of the last few years in this field and indicates some future directions >

Multiple quantum well (MQW) waveguide modulators

Gallium‐nitride single crystals were grown on (0001)‐ and (0112)‐oriented sapphire substrates by metalorganic vapor‐phase epitaxy. Smooth‐surfaced layers with fine ridgelike facets can be obtained on the (0112) sapphire. They have lower carrier concentrations than the layers on the (0001) sapphire. Deep centers responsible for blue (∼425 nm) and yellow (∼560 nm) emissions from undoped layers are reduced on the (0112) substrates, as compared with the (0001) substrates. On the other hand, the layers on the (0001) sapphire have better crystallinity and higher Zn‐incorporation efficiency than those on the (0112) sapphire. Growth kinetics of GaN layers are discussed by developing a tentative model.

Substrate‐orientation dependence of GaN single‐crystal films grown by metalorganic vapor‐phase epitaxy

Methanolysis of {t-Bu2In[μ-P(SiMe3)2]}2 (1) in aromatic solvents gives polycrystalline InP fibers (dimensions 10−100 nm × 50−1000 nm) at 111−203 °C. The chemical pathway consists of a molecular component, in which precursor substituents are eliminated, and a nonmolecular component, in which the InP crystal lattices are assembled. The two components working in concert comprise the solution−liquid−solid (SLS) mechanism. The molecular component proceeds through a sequence of isolated and fully characterized intermediates:  1 → [t-Bu2In(μ-OMe)]2 (2) → [t-Bu2In(μ-PHSiMe3)]2 (3) → 2 → [t-Bu2In(μ-PH2)]3 (4). Complex 4, which is alternatively prepared from t-Bu3In and PH3, undergoes alkane elimination, the last steps of which are catalyzed by the protic reagent MeOH, PhSH, Et2NH, or PhCO2H. In the subsequent nonmolecular component of the pathway, the resulting (InP)n fragments dissolve into a dispersion of molten In droplets, and recrystallize as the InP fibers. Important criteria are identified for crystal growt...

Solution−Liquid−Solid Growth of Indium Phosphide Fibers from Organometallic Precursors: Elucidation of Molecular and Nonmolecular Components of the Pathway

The metalorganic chemical vapor deposition (MOCVD) of epitaxial III‐V semiconductor alloys on III‐V substrates is reviewed in detail. The emphasis is placed on both practical and theoretical knowledge of the equipment and deposition process. The chemistry of the source alkyls and the dynamics of the transport process are discussed. The growth of the GaAs and AlxGa1−xAs systems are treated as prototypical examples (and the most studied) of the III‐V materials. Latter sections review InP, Ga1−xInxAs, and related alloys. Finally, the antimonide and the other systems are reviewed. Electronic and optical devices fabricated from MOCVD‐grown materials are used as examples of the capabilities of the growth technique.

M. J. Ludowise

Papers

Metalorganic chemical vapor deposition of III‐V semiconductors