Chang-Sik Son

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.

Electrical Properties of Heavily Carbon-Doped GaAs Epilayers Grown by Atmospheric Pressure Metalorganic Chemical Vapor Deposition Using CBr4

Heavily carbon (C)-doped GaAs epilayers with hole concentrations as high as 3.1 x 10 20 cm -3 were grown by atmospheric pressure metalorganic chemical vapor deposition using CBr 4 as the dopant source. The electrical properties of C-doped GaAs epilayers simultaneously grown on exact and 2° off (100) GaAs substrates were investigated. The hole concentration in the epilayer grown on the exact (100) substrate was higher than that in the epilayer on the 2° off (100) substrate grown under equivalent conditions. The hole concentration for the exact (100) substrates exhibited saturation as the growth temperature increased. The hole concentration for the 2° off (100) substrates exhibited thermal activation behavior. The activation energy of the hole concentration as a function of the growth temperature did not change significantly regardless of the V/III ratio (E a ∼ 63 and 71 kcal/mol). The higher desorption rate of C-containing species due to the higher adsorption rate of AsH x species on the 2° off (100) substrate, which has a higher step density than the exact (100) substrate, is responsible for this thermal activation behavior.

MASKLESS SELECTIVE EPITAXIAL GROWTH ON PATTERNED GAAS SUBSTRATES BY METALORGANIC CHEMICAL VAPOR DEPOSITION

Maskless one-step selective CCl4-doped GaAs epilayers have been grown on patterned GaAs substrates by atmospheric pressure metalorganic chemical vapor deposition. The growth technique has potential for realizing a well-defined quantum confinement structure and lateral structure device. Round shaped CCl4-doped GaAs epilayer was selectively grown inside a U-groove and on the sidewalls of a mesa with a significant lateral growth rate enhancement, whereas no growth was observed outside U-groove and on top of the mesa.

Effect of RF Power on Structural and Electrical Properties of Ga-Doped ZnO for Transparent Electrode of Thin Film Solar Cells

Abstract We have investigated the structural and electrical properties of Ga-doped ZnO (GZO) thin films deposited by anRF magnetron sputtering at various RF powers from 50 to 90 W. All the GZO thin films are grown as a hexagonal wurtzitephase with highly c-axis preferred parameters. The structural and electrical properties are strongly related to the RF power. Thegrain size increases as the RF power increases since the columnar growth of GZO thin film is enhanced at an elevated RFpower. This result means that the crystallinity of GZO is improved as the RF power increases. The resistivity of GZO rapidlydecreases as the RF power increases up to 70 W and saturates to 90 W. In contrast, the electron concentration of GZO increasesas the RF power increases up to 70 W and saturates to 90 W. GZO thin film shows the lowest resistivity of 2.2×10 −4 Ωcmand the highest electron concentration of 1.7×10 21 cm −3 at 90 W. The mobility of GZO increases as the RF power increasessince the grain boundary scattering decreases due to the reduced density of the grain boundary at a high RF power. Thetransmittance of GZO thin films in the visible range is above 90%. GZO is a feasible transparent electrode for application asa transparent electrode for thin film solar cells.Key wordsGa, ZnO, RF power, resistivity, sputtering.

Growth and Characterization of Triangular InGaAs/GaAs Quantum Wire Structures Grown by Low-Pressure Metalorganic Chemical Vapor Deposition

Noble quantum wire structures were grown by low-pressure metalorganic chemical vapor deposition (MOCVD). Triangular InGaAs/GaAs quantum wire structures with sharp tips and smooth sidewalls were grown on SiO2 masked GaAs substrates. To characterize and analyze the selectively grown structures, scanning electron microscopy and temperature-dependent photoluminescence were used. Even though the opening width was different, it was possible to obtain a similar triangular structure. If we use this quantum confined structure of different size, it would be possible to grow quantum wire structures with various thicknesses and fabricate uniquely integrated optical devices which include light-emitting sources of multiple wavelength. The emission peak from quantum wires was observed at 975 nm. With increasing temperature, the emission intensity from side wall quantum wells decreased abruptly. However, the intensity from quantum wires decreased slowly compared to that from side wall quantum wells and it became even stronger above 50 K. The possible carrier capture processes in the quantum wire structures were also discussed.

Terahertz Electromagnetic Wave Generation from Quantum Nanostructure

We have investigated terahertz (THz) electromagnetic wave generation from semiconductor quantum nanostructures.The samples used in our experiment are a GaAs/AlGaAs symmetric triple-coupled quantum well and a GaAs/AlGaAs crescent-shaped quantum wire. The THz electromagnetic waves were generated by ultrashort optical pulse excitation and detected by a spatial electrooptic (EO) sampling method. Generation of a THz electromagnetic wave, which originats from quantum beats with three frequency components of 0.8, 1.0, and 1.8 THz, was observed in the symmetric triple-coupled quantum well. In a quantum wire, THz electromagnetic wave generation due to the instantaneous polarization accompanied by the creation of excitons by ultrashort optical pulse excitation was observed.

Effect of Yellow Phosphor on Characteristics of White Light Emitting Diode

We have investigated the optical and electrical properties of surface mounted white light emitting diode (LED) chips prepared by using yellow phosphors on the blue LED chip. The yellow phosphor mixed with transparent epoxy was coated on the prepared LED chip. The optimum mixing conditions with epoxy and yellow phosphor is obtained at the mixing ratio of epoxy:yellow phosphor = 97:3 wt%. The maximum luminance and light emitting efficiency are above and 23.2 lm/W, respectively, at the bias voltage of 2.9 V. There was no distinct change in the luminance strength with changing of the yellow phosphor ratios. The current of the white LED chip is about 30 mA at 2.9 V.

High-Density Quantum Nanostructure for Single Mode Distributed Feedback Semiconductor Lasers by One-Step Growth

We have developed a new way of the constant growth technique to maintain a grating height of originally-etched V-groove of submicron gratings up to 1.5 thickness by a low pressure metalorganic chemical vapor deposition. The constant growth technique is well performed on two kinds of submicron gratings that made by holography and electron (e)-beam lithography GaAs buffer layer grown on thermally deformed submicron gratings has an important role in recovering the deformed grating profile from sinusoidal to V-shaped by reducing mass transport effects. The thermal deformation effect on submicron gratings made by e-beam lithography is less than that on submicron gratings made by holography. The constant growth technique is an important step to realize complex optoelectronic devices such as one-step grown distributed feedback lasers and two-dimensional photonic crystals.

One-dimensional Array of Inks Quantum Dots on Grown V-grooves

One-dimensional array of InAs quantum dots (QDs) have been grown on V-grooved GaAs substrates by low-pressure metalorganic chemical vapor deposition. Atomic force microscope images show that InAs QDs are aligned in one-dimensional rows along the ［011］oriented bottom of V-grooves and no QDs are formed on the sidewalls and the surface of mesa top. Capability to grow one-dimensional InAs QDs array would feasible for the single electron tunneling devices and other novel quantum-confined devices.

Heavy Carbon Incorporation into High-Index GaAs

Heavily -typed ( ) GaAs epilayers have been grown on high-index GaAs substrates with various crystallographic orientations from (100) to (111)A by a low-pressure metalorganic chemical vapor deposition. Carbon (C) tetrabromide (CBr) was used as a C source. At moderate growth temperatures and high V/III ratios, the hole concentration of C-doped GaAs epilayers shows the crystallographic orientation dependence. The bonding strength of As sites on a growing surface plays an important role in the C incorporation into the high-index GaAs substrates.