M. Konuma

Adhesion in growth of defect‐free silicon over silicon oxide

By applying liquid phase epitaxy, we have grown defect‐free silicon and silicon–germanium layers on partially oxide‐masked Si wafers. The growth of the layers started epitaxially in oxide‐free seeding areas and proceeded laterally over the thermal oxide film. Detailed studies by x‐ray topography and electron microscopy show that the obtained thin semiconductor‐on‐insulator layers bend towards the oxide during lateral growth. The bending of the layers can be ascribed to adhesion and interfacial forces. Adhesion operates across a gap between the closely spaced surfaces of the oxide and the epitaxial Si and facilitates lateral growth of high‐quality semiconductor layers on dissimilar layers or substrates. The technical potential of adhesion‐dependent solution growth on dissimilar substrates is discussed.

Solution growth of epitaxial semiconductor-on-insulator layers

Abstract We have grown defect-free semiconductor-on-insulator (SOI) layers by liquid phase epitaxy. Defect-free Si layers grow laterally over SiO 2 by starting from seeding windows or ridge seeds on selectively oxide-masked (111) Si substrates. Growth is terminated when {111} facets at the sidewalls develop. The thin SOI layers are slightly bent in relation to the substrate and adhere firmly to the oxide film. The surface of defect-free SOI layers is formed by a perfect (111) facet, whereas monoatomic steps are found at the interfacial bottom of the layers. Although the Si layers are slightly bent, layers grown from different seeds may coalesce defect-free with seams of up to 150 μm in length. In SiGe layers on patterned Si substrates misfit and threading dislocations promote vertical growth of relaxed layers; SiGe layers grown laterally over oxide-covered Si substrates contain only few dislocations.

Growth of multi-crystalline silicon on seeded glass from metallic solutions

Abstract Crystalline Si was grown on substrates of fused quartz, borosilicate, and sodalime glass. The glass substrates were initially coated with a seeding layer of thin nano-crystalline silicon. The nano-crystalline Si was deposited by plasma processes from a mixture of SiH 4 H 4 gas. Then, on the seeding layer, crystalline Si was grown from a metallic solution of In or Ga solvent which was saturated with Si. The grains in the solution-grown Si reached sizes up to 100 μm. The properties of the crystalline silicon on glass are described.

SiGe Thin-Film Structures for Solar Cells

In order to study their applicability as the active base material in Si thin crystalline film solar cell technology, SiGe relaxed layers grown by Liquid Phase Epitaxy (LPE) and Chemical Vapor Deposition (CVD) on Si substrates are investigated by optical and electrical measurements (TEM, EXD, PL, EBIC). The main results of this work is to point out the improvement of the SiGe active base layer by using smooth Ge graded SiGe buffer layer and remote plasma hydrogenation. TEM, EXD, PL experiments show the effect of the Ge graded buffer layer grown using LPE, by confining the threading dislocations in the SiGe buffer layer close to the Si/SiGe interface. EBIC measurements reveal low recombination activity of dislocations at 300 K providing the diffusion length exceeds the 15 {micro}m layer thickness. The enhanced luminescence of SiGe near bandgap indicates that remote plasma hydrogenation induces a decrease of the non-radiative recombination pathways due to dislocations on CVD layers where defect recombinations dominate as indicated by EBIC measurements. This study points out the importance of controlling relaxed SiGe layers with good minority carrier recombination quality as a key issue for the optimization of new SiGe/Si based solar cells.

Electrical properties of SiGe layers grown by LPE and CVD

In this paper we present electrical properties of a few microns thick, relaxed SiGe layers for solar cell application. The layers were characterized by means of electron beam induced current (EBIC), X-ray microanalysis (EDX), backscattered electrons, and Hall effect analysis.

Centrifugal techniques for solution growth of semiconductor layers

Two centrifugal techniques, I and II, have been applied to grow semiconductor layers in a rotating crucible. Technique I employs centrifugal forces to transport the solutions in the liquid phase epitaxial process. Layers of Si and SiGe grown on 100 mm diameter Si wafers and of GaAs on GaAs substrates outlined the capability and potentialities of technique I. Technique II requires higher rotational frequencies of the crucible. The higher centrifugal forces available in this technique influence the local distribution of the solute in the solvent. Locally increased solute concentration in the solution allows us to prepare multicrystalline self-supporting and inclusion-free films, or to prepare thick homo- and hetero-epitaxial LPE layers even on dissimilar substrates. We describe, in this paper, experimental results obtained by growing SiGe layers on 100 mm single-crystalline Si wafers using centrifugal technique I. We describe also the first results obtained by centrifugal technique II, and thereby focus on self-supporting multicrystalline sheets of Si, SiGe, and GaAs, and on multicrystalline Ge layers grown on sintered porous quartz substrates.