Min-Suk Lee

Characterization of the oxidized indium thin films with thermal oxidation

Abstract Oxidized indium thin films on several substrates were formed by indium deposition and thermal oxidation. The oxidation was carried out in oxygen ambient at temperatures ranging from 500 to 900°C for 1 h. In the scanning electron microscopy measurements, the oxidized indium films were shown to be composed of grains with sizes of 400 to 600 nm which agglomerate subgrains with diameters of 40–60 nm. From the measurements of X-ray diffraction, X-ray photoelectron spectroscopy and Auger electron spectroscopy, it was confirmed that the oxidized indium are cubic indium oxide (In 2 O 3 ) polycrystallites. In addition, no elements other than In and O atoms were found from secondary ion mass spectroscopy measurements. A strong orange photoluminescence, peaking at 637 nm, was observed at room temperature for these films. It was assumed that a center of orange luminescence in the indium oxide films may be related to oxygen deficiencies or defects.

Visible luminescences from thermally grown silicon dioxide thin films

We introduce visible photoluminescences (PL) of violet (432 nm) and yellow (561 nm) at room temperature from thermally treated silicon dioxide thin films. These luminescences were very strong with a near infinite degradation time. At an oxide layer thickness less than 200 nm, these luminescences were not seen, even with high temperature annealing at about 1000 °C. As a result of photoluminescence, x‐ray photoelectron spectroscopy, Fourier transform infrared, and high‐resolution transmission electron microscopy measurements, we conclude that the violet PL originates from the nanocrystalline silicon formed in the silicon oxide film by the thermal strain effect between the silicon substrate and the silicon dioxide film, while the yellow PL originates from the radiative decay of self‐trapped excitons that are confined to oxygen sufficient structures.

The facet evolution during metalorganic vapor phase epitaxial growth on V-grooved high Miller index GaAs substrates

Abstract The facet evoluting during metalorganic vapor phase epitaxial (MOVPE) growth on high Miller index V-grooved GaAs substrates with (1311)A, (511)A, (311)A, and (211)A as well as (100) orientations, has been investigated. The {433}A and (100) facets evolved on the as-etched V-grooved substrate having {111}A side walls, regardless of substrate orientation. As the substrate orientation is tilted toward (211)A, the (433)A facet on the long-side wall is extended, while the length of the newly formed (100) facet on the other side is reduced. The (4⦶3⦶3) facet on the short-side wall formed in the early stage of growth diminishes more rapidly. The direction of the locus line of the intersection points between the two facets is initially [100]. However, this direction eventually changes after the (4⦶3⦶3)A facet on the short-side wall disappears. The growth rate properties of the facets can be explained by channel effect and different surface mobilities of different species.

Temperature dependent electrical properties of heavily carbon-doped GaAs grown by low-pressure metalorganic chemical vapor deposition

Abstract The temperature dependence of the electrical properties of heavily carbon (C)-doped GaAs has been analyzed by Van der Pauw-Hall measurements. All samples were grown by low-pressure metalorganic chemical vapor deposition (MOCVD). At low temperature range (T 100 K) the mobility values were decreased due to lattice phonon scattering. With decreasing the temperature, the carrier concentration was nearly the same, and even at low temperature range the carrier concentration was not frozen out. The resistivity increased at high temperature due to decreased mobility, but it did not increase in the low temperature range. All these electrical properties proved the degenerate conduction of heavily C-doped GaAs. The temperature dependence of mobility was analyzed using a simple analytical equation in the strongly degenerate limit and with constant effective mass. There was no compensation in the C-doped GaAs epilayer with p = 4.25 × 1019cm−3, however there was some compensation ( θ = N d N a = 0.02 ) in the epilayer with p = 1.01 × 1020cm−3. Thus it is suggested that heavily C-doped GaAs grown by low-pressure MOCVD exhibits a little or no compensation in the epilayers, and our simple analysis can explain the temperature dependence of Hall mobility of heavily C-doped GaAs epilayer very well.

Properties of carbon-doped InGaAs grown by atmospheric pressure metalorganic chemical vapor deposition using CCL4

Abstract This paper shows the results of a van der Pauw-Hall analysis of carbon-doped InGaAs epilayers grown by atmospheric pressure metalorganic chemical vapor deposition using CCl 4 gas. Heavily C-doped In x Ga 1 − x As ( x = 0 to 0.52) epilayers were obtained by varying the V III ratio from 1.3 to 32 and at a low growth temperature of 550°C, while keeping the flow rate of CCl 4 constant. For up to an InAs mole fraction of 0.43, a hole concentration of about 1.1 × 10 19 cm −3 was obtained. In the case of as-grown samples, a type conversion from p-type to n-type to n-type occurred at an InAs mole fraction of 0.48. This work also describes the effects of a rapid thermal annealing (RTA) on the electrical properties, particularly on a type conversion of InGaAs. After the RTA process at an annealing temperature of 750°C for 5 s, as-grown In 0.44 Ga 0.56 As with the p-type of 5.6 × 10 17 cm −3 was converted into the n-type of 3.9 × 10 17 cm −3 . This can be attributed to the breaking of the CH or CH x bonds after the RTA process. The broken carbon atoms could enter into arsenic sites or indium (or gallium) sites in the epilayers. With increasing InAs mole fraction, more carbon atoms were supposed to enter into indium sites rather than arsenic sites, due to a lower binding energy of InC than that of AsC.

Growth behavior on V-grooved high Miller index GaAs substrates by metalorganic chemical vapor deposition

Abstract The growth behavior of GaAs AlGaAs during metalorganic chemical vapor deposition (MOCVD) on V-grooved GaAs(311)A substrates, specifically its dependence on growth temperature and V III ratio, has been investigated. A new (100) facet has evolved at the outer edge of the short side wall of the groove. The length of this facet decreases with increasing the growth temperature and reducing the V III ratio. The phenomena can be explained by the surface mobility or incorporation rate dependence of group III species on each facet as it appeared in this study. The best surface morphology has been obtained at 750°C. The newly evolved (100) facet has a defect free surface. Photoluminescence (PL) measurements have been carried out after growing 2 kinds of GaAs quantum wells (QWLs) on the patterned (311)A substrates. In the case of QWLs with a thick AlGaAs buffer layer, 3 peaks from the (100), (433)A and (311)A planes have been identified, while the (100) peak was not detected in the case of a thin buffer layer.

The role of a thin amorphous silicon layer in the fabrication of micro-pored silicon

Abstract Micro-pored silicon formed by electrochemical anodization of a p-type (100) Si wafer with a thin amorphous Si (a-Si) layer showed green colored photoluminescence (PL) at room temperature. The a-Si thin films were deposited on an Si(100) wafer by rf magnetron sputtering. The wafers with and without a-Si layer were electrochemically anodized and annealed by a rapid thermal process at 800 °C for 10 min. A strong green PL signal peaked at 543 nm appeared in the samples fabricated with a-Si thin film, while normally processed porous Si samples showed only a typical PL signal at 681 nm. From scanning electron microscopy, Auger electron spectroscopy, and Fourier transformed infra-red spectroscopy, it is suggested that the a-Si layer has the role of a mesh for the smooth and fine Si porosity which prevents oxidation during the anodization of the Si substrate.

InGaAs layer effect on the growth of AlGaAs/GaAs quantum wires on V-grooved InGaAs/GaAs substrates

Abstract An effect of InGaAs layer on the growth of AlGaAs GaAs quantum wires (QWRs) on V-grooved InGaAs GaAs (1 0 0) substrates has been studied. The structures are grown by atmospheric pressure metalorganic chemical deposition (MOCVD) and characterized with scanning electron microscope, transmission electron microscope and photoluminescence (PL) measurements. The thick InGaAs layer causes to form several facets in the side walls of V-grooves. Especially, the side walls near the bottom are convexly shaped, resulting in narrowing the width near the bottom of V-groove. QWRs grown on this substrate show a blue shift in the PL spectra, while any PL signal from the top-QWLs on InGaAs layer is not obtained. These results may be originated from the narrowing effect of the InGaAs layer on the bottom and from the poor crystallinity of the top epilayer on the InGaAs layer with many dislocations.

InGaAs layer effect on the growth of AlGaAs/GaAs quantum wires on V-grooved GaAs substrates

Abstract We have studied an effect of InGaAs layer on the structural and optical properties of AlGaAs/GaAs quantum wires (QWRs) grown on V-grooved GaAs(100) substrates by metalorganic chemical vapor deposition. The In0.15Ga0.85As layer with thickness of 2–4 μm were prepared on GaAs(100) substrates, and the V-grooves were defined with 20 μm intervals by photolithographic method. The quantum structures with five periods of 5 nm GaAs and 25 nm Al0.5Ga0.5As layers were grown on V-grooved InGaAs/GaAs substrates. From the scanning electron microscope and transmission electron microscope measurements, it appeared that the thick InGaAs layer caused to form several facets in the side walls of V-grooves. Especially, the side walls near the bottom were convexly shaped, resulting in narrowing the width near the bottom of the V-groove. In the photoluminescence (PL) spectra, QWRs grown on this substrate showed a blue shift, while any PL signal from the top-quantum wells on InGaAs layer has not appeared. From these results, it was suggested that the InGaAs layer plays an important role for the lateral tightening of QWRs.