• Analytical Science and Technology
• /
• v.5 no.2
• /
• pp.213-216
• /
• 1992

Semiinsulating GaAs crystals employing LPLEC technique should be grown from the Ga-rich melt due to a very low incorporation of unintentional impurities such as carbon (<$10^{15}cm^{-3}$). High resisitivity of this material can be derived from the balanced compensation among not only EL2 deep donors and carbon acceptors but also H1 double charge native acceptors(Ev + 77meV, Ev + 200 meV) and H2 native acceptors(Ev + 68 meV). Considering of the complicated compensation mechanism using statistical calculation of the electron occupancy of each level, SI GaAs crystal with low impurity contents(<$10^{15}cm^{-3}$) can be successfully obtained by maintaining the melt composition around 0.45 As mole fraction.

• Journal of the Korean Electrochemical Society
• /
• v.17 no.1
• /
• pp.1-6
• /
• 2014

This review article summarizes photoelectrochemical water splitting using gallium nitride (GaN). GaN materials have been studied as novel photoelectrode material due to its chemical stability and easy band gap engineering. Unlike other semiconductor materials that are easily corroded in strongly acidic or alkaline electrolyte, n-type GaN is chemically stable enough to be used as photoanode in oxygen evolution reaction. Furthermore, studies on p-type GaN have been recently reported. This review briefly discusses problems that need to be solved before GaN materials find widespread use in solar fuel application.

• Proceedings of the Optical Society of Korea Conference
• /
• 1989.02a
• /
• pp.196-200
• /
• 1989

The physical properties related to the GaInAs/InP crystal grown by LPE are discussed in terms of both the design and operation characteristics of the GaInAs/InP Pin photodiode has cutoff frequency of 358 MHz and responsivity, 0.53 A/W (λ=1.3${\mu}{\textrm}{m}$), with dark current density as low as 4$\times$10-4/$\textrm{cm}^2$ under reverse bias voltage of 5V.

• Proceedings of the KIEE Conference
• /
• 1994.07b
• /
• pp.1216-1219
• /
• 1994

A reflection type SEED from LP-MOCVD grown InGaAs/GaAs ESQW structures, with 5% In fraction, has been fabricated and its basic characteristics were investigated. Its intrinsic region consists of 50 pairs of alternating $100{\AA}$ $In_{0.05}Ga_{0.95}As$ barrier and $100{\AA}$ GaAs layers. And a multilayer reflector stack of $Al_{0.12}Ga_{0.88}As(641{\AA})-/AlAs(774{\AA})$ was vertically integrated below the p-i-n structures. The device processing includes the mesa etching, insulator deposition, indium metallization, and thermal alloy for Ohmic contact. Photocurrent spectrum measurement showed the exciton absorption peak at 905nm and availability as a optical switching device. This device showed a contrast ratio of 2:1 by the reflectance spectrum measurement.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.24 no.1
• /
• pp.8-14
• /
• 2014

In this study, we investigated synthesis and characteristics of gallium oxide ($Ga_2O_3$) powders prepared by precipitation method. $Ga_2O_3$ powders were synthesized using $Ga(NO_3)_3$ as a starting material and $NH_4OH$ as a precipitant. The oxidation temperature of $Ga(OH)_3$ and phase transition temperature of $Ga_2O_3$ was revealed using TG-DSC analysis. The crystal structural change of $Ga_2O_3$ powders was investigated by XRD analysis. The morphologies and size distributions of $Ga_2O_3$ particles were analyzed using SEM.

• Korean Journal of Materials Research
• /
• v.14 no.4
• /
• pp.235-238
• /
• 2004

The LT-MBE (low temperature molecular beam epitaxy) allows to dope GaAs with Mn over its solubility limit. A 75 urn thick GaMnAs layers are grown on a low temperature grown LT-GaAs buffer layer at a substrate temperature of $260^{\circ}C$ by varying Mn contents ranged from 0.03 to 0.05. The typical growth rate for GaMnAs layer is fixed at 0.97 $\mu\textrm{m}$/h and the V/III ratio is varied from 25 to 34. The electrical and magnetic properties are investigated by Hall effect and superconducting quantum interference device(SQUID) measurements, respectively. Double crystal X-ray diffraction(DCXRD) is also performed to investigate the crystallinity of GaMnAs layers. The $T_{c}$ of the $Ga_{l-x}$ /$Mn_{x}$ As films grown by LT-MBE are enhanced from 38 K to 65 K as x increases from 0.03 into 0.05 whereas the $T_{c}$ becomes lower to 45 K when the V/III ratio increases up to 34 at the same composition of x=0.05. This means that the ferromagnetic exchange coupling between Mn-ion and a hole is affected by the growth condition of the enhanced V/III ratio in which the excess-As and As-antisite defects may be easily incorporated into GaMnAs layer.

• Journal of Veterinary Clinics
• /
• v.19 no.3
• /
• pp.316-321
• /
• 2002

The purpose of this study was to examine the effect of Ga-As(Gallium-Arsenide, wave length; 904 nm) infrared laser irradiation on healing of the experimentally crush injured rat sciatic nerves. The bilateral sciatic nerves of 43 adult male Sprague-Dawley rats were compressed surgically with a straight hemostat (1 mm width). The right legs of all the rats were irradiated using a 27 mW Ga-As infrared laser (laser irradiated group). The radiation procedure was administered for 3 minutes every day for 1, 3, 5, and 7 weeks in each group. Left legs were not irradiated and served as the control group. The numbers of total myelinated axon and degenerated myelin in the sciatic nerves of bilateral legs were measured and analyzed with mage analysis system in order to make a morphological analysis of the effect of the Ga-As infrared laser on injured nerves. Total number of myelinated axons was increased with time interval, especially in the 1, 3. and 5 week of irradiated group. Conversely, the number of degenerated myelin was decreased with time interval, especially in the irradiated group. The effects in the irradiated group were more pronounced than those of the control group. In conclusion, the Ga-As infrared laser irradiation is a useful adjuvant therapy to the regeneration of the peripheral nerve injury.

• Korean Journal of Materials Research
• /
• v.20 no.4
• /
• pp.199-203
• /
• 2010

Hybridization of semiconductor materials with carbon nanotubes (CNTs) is a recent field of interest in which new nanodevice fabrication and applications are expected. In this work, nanowire type GaAs structures are synthesized on porous single-wall carbon nanotubes (SWCNTs) as templates using the molecular beam epitaxy (MBE) technique. The field emission properties of the as-synthesized products were investigated to suggest their potential applications as cold electron sources, as well. The SWCNT template was synthesized by the arc-discharge method. SWCNT samples were heat-treated at $400^{\circ}C$ under an $N_2/O_2$ atmosphere to remove amorphous carbon. After heat treatment, GaAs was grown on the SWCNT template. The growth conditions of the GaAs in the MBE system were set by changing the growth temperatures from $400^{\circ}C$ to $600^{\circ}C$. The morphology of the GaAs synthesized on the SWCNTs strongly depends on the substrate temperature. Namely, nano-crystalline beads of GaAs are formed on the CNTs under $500^{\circ}C$, while nanowire structures begin to form on the beads above $600^{\circ}C$. The crystal qualities of GaAs and SWCNT were examined by X-ray diffraction and Raman spectra. The field emission properties of the synthesized GaAs nanowires were also investigated and a low turn-on field of $2.0\;V/{\mu}m$ was achieved. But, the turn-on field was increased in the second and third measurements. It is thought that arsenic atoms were evaporated during the measurement of the field emission.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.11
• /
• pp.1056-1060
• /
• 2005

We investigated the fabrication and characteristics of the nitride-based spin-polarized LEDs with room-temperature ferromagnetic (Ga,Mn)N layer as a spin injection source. The (Ga,Mn)N thin films having room-temperature ferromagnetic ordering were found to exhibit the negative MR and anomalous Hall resistance up to room temperature, revealing the existence of spin-polarized electrons in (Ga,Mn)N films at room temperature. The electrical characteristics in the spin LEDs did not degraded in spite of the insertion of the (Ga,Mn)N layer into the LED structure. In EL spectra of the spin LEDs, it is confirmed that the devices produce intense EL emission at 7 K as well as room temperature. These results are expected to open up new opportunities to realize room-temperature operating semiconductor spintronic devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.05a
• /
• pp.150-152
• /
• 2005

We investigated the fabrication and characteristics of spin-polarized LEDs based on GaN using (Ga,Mn)N as spin injection source. (Ga,Mn)N thin films were found to exhibit the ferromagnetic ordering above room temperature and the negative MR up to room temperature. The electrical characteristics in spin LEDs did not degraded in spite of the insertion of (Ga,Mn)N films. In EL spectra of spin LEDs, it is confirmed that spin LEDs emit the strong light at 7 K as well as room temperature. These results suggest that it is possible to emit spin-polarized light in our spin LEDs.