• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.405-408
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• 1998

Due to the large conduction band discontinuity between emitter base, OmGaAs HBT has an advantge to enable the hot electrons to inject into the base. In this paper, InAlGaAs/InGaAs HBT with the various emitter junction gradings and the modified collectors are simulated and analyzed by HMC(hybrid monte carlo) simulator in order to find a optimal structure for the shortest transit time. A minium base transit time (.tau.$_{b}$ ) of 0.21 ps was obtained for HBT with the grading layer, which is parabolically graded from x=1.0 to x=0.5. The minimum collector transit time (.tau.$_{c}$ ) of 0.31ps was found when the collector was modified by inserting p$^{[-10]}$ and p$^{+}$ layers. Thus HBT in combination with the emitter grading and the modified collector layer showed the cut-off frequency (f$_{T}$) of 183GHz.z.z.

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.25-28
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• 2001

In this paper, we have investigated the effects of gas flow rate, rf power, process pressure and Ar addition on reactive ion etching of InP, InGaAs and InAlAs using Sic14 and Cl$_2$ gases. The etch rates were measured by using a surface profiler. The etched profiles, sidewall roughness, and surface morphology were observed by scanning electron microscopy and by atomic force microscopy. The selective etching of InGaAs to InP and InAlAs was studied by varying the etching parameters. It was found that Cl$_2$ gas is more efficient for the selective etching of InGaAs to InAlAs than SiCl$_4$ gas. The etch selectivity of InGaAs to InAlAs is strongly dependent on the rf power and the process pressure.

• Journal of the Korean Society of Physical Medicine
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• v.9 no.4
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• pp.433-438
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• 2014

PURPOSE: The purpose of our study was to compare a 975-nm, 500-mW GaAlAs low-level laser therapy versus placebo low-level laser therapy with regard to the immediate changes on the myofascial trigger point of the dominant upper trapezius muscle in subjects with rounded shoulder posture. METHODS: Thirty-two male college students with rounded shoulder posture and shoulder pain consented to participate in the experiment. The subjects were randomly assigned to a 2-minute procedure with either an active GaAlAs low-level laser or a placebo GaAlAs low-level laser. The pressure-pain threshold and visual analog scale on tenderness at 3 kg were measured with an algometer before and after the laser treatments. RESULTS: The active GaAlAs low-level laser group showed significant changes in pressure-pain threshold and visual analog scale on tenderness at 3 kg (p<0.05). The placebo GaAlAs low-level laser group showed no significant changes in either pressure-pain threshold or visual analog scale on tenderness at 3 kg (p>0.05). CONCLUSION: An immediate effect was observed in pressure-pain threshold and visual analog scale on tenderness at 3 kg following a 2-minute application ($857.14J/cm^2$) of a 975-nm, 500-mW GaAlAs low-level laser to the myofascial trigger point of the dominant upper trapezius muscle in patients with rounded shoulder posture.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.5
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• pp.431-435
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• 2009

The apparatus has been fabricated using the laser diode and microprocessor unit. The apparatus used a InGaAlP laser diode for laser medical therapy and was designed for a pulse width modulation type to increase stimulation effects. To raise the stimulus effect of the human body, the optical irradiation frequency could be set up. The study has executed in-vivo experiment by employing our own developed laser diode irradiation system to investigate the effects of the InGaAlP laser diode irradiation on the wound healing as a preliminary study aimed at the application of InGaAlP laser diode to wound healing of human skin injury. The study cut out whole skin layers of Sprague-Dawley rat on the back part in 1 cm circle and observed developing effects after executing light irradiation for 9 days, and in result it is found that the light irradiation rat showed earlier wound healing than non-irradiation rat during the experimental period. In addition, there are some differences found regarding the healing process between laser diode irradiated rats and non-irradiated ones.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.194.2-194.2
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• 2015

본 논문에서는 InP 기판에 자발형성법 (Self-assembled Mode)으로 성장한 InAs/InAlGaAs 양자점(Quantum Dots)의 외부 열처리 온도에 따른 광학적 특성을 논의한다. 분자선증착기 (Molecular Beam Epitaxy, VH80MBE)로 5주기 적층구조를 갖는 InAs/InAlGaAs 양자점 시료 (기준시료)를 성장 후 온도 의존성 및 여기광세기 의존성 포토루미네슨스 (photoluminescence, PL) 분광법으로 기본특성을 평가하였다. 양자점 시료를 $500{\sim}800^{\circ}C$에서 열처리를 수행하고 광학적 특성을 열처리 전과 비교하여 분석하였다. $550^{\circ}C$에서 열처리한 InAs/InAlGaAs 양자점 시료의 저온 (11K) PL 파장은 1465 nm를 보였으며, 이는 열처리를 하지 않은 기준시료의 1452 nm 보다 13 nm 장파장으로 이동하였다. 열처리 온도가 $700^{\circ}C$ 이상인 경우, 양자점 PL 파장이 다시 단파장으로 이동하는 현상을 보였지만 여전히 열처리하지 않은 기준시료보다 장파장을 나타내었다. $700^{\circ}C$에서 열처리한 양자점 시료의 저온 PL 광세기는 기준시료보다 15.5배 더 크게 나타났으며, 주변 온도가 증가할수록 더디게 감소하는 것을 확인할 수 있었다. 온도의존성 PL로부터 구한 활성화에너지 (Activation Energy)는 $700^{\circ}C$ 열처리 온도의 경우 175.9 meV를 나타내었다. InAs/InAlGaAs 양자점 시료의 열처리 온도에 따른 광특성 변화를 InAs 양자점과 InAlGaAs 장벽층 계면에서 III족 원소인 In, Al 및 Ga의 상호확산과 결함이 완화되는 현상으로 해석할 수 있다.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.2
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• pp.111-115
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• 2001

Metamorphic InAlAs/InGaAs HEMT are successfully demonstrated, exhibiting several advantages over conventional P-HEMT on GaAs and LM-HEMT on InP substrate. The strain-relaxed metamorphic structure is grown by MBE on the GaAs substrate with the inverse-step graded InAlAs metamorphic buffer. The device with 40% indium content shows the better characteristics than the device with 53% indium content. The fabricated metamorphic HEMT with $0.2\mu\textrm{m}$T-gate and 40% indium content shows the excellent DC and microwave characteristics of $V_{th}-0.65V,{\;}g_{m,max}=620{\;}mS/mm,{\;}f_T120GHZ{\;}and{\;}f_{max}=210GHZ$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.73-73
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• 2005

• Journal of Korean Vacuum Science & Technology
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• v.6 no.2
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• pp.58-61
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• 2002

Photoluminescence up-conversion in semiconductor heterostructures is a phenomenon in which luminescence occurs at energies higher than that of the excitation photons. It has been observed in many semiconductor heterostructure systems, including InP/AnALAs, CdTe/CdMgTe, GaAs/ordered-(Al)GalnP, GaAs/AIGaAs, and InAs/GaAs. In this wort, GaAs/AIGaAs heterostructures are used as a model system to study the mechanism of the up-conversion process. This system is ideal for testing different models because the band offsets are quite well documented. Different heterostructures are designed to study the effect of disorder on the up-converted luminescence efficiency. In order to study the roles of different types of carriers, the effect of doping was investigated. It was found that the up-converted luminescence is significantly enhanced by p-type doping of the higher-band-gap material.

• Korean Journal of Optics and Photonics
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• v.32 no.2
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• pp.55-61
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• 2021

The lateral-mode characteristics of 850-nm GaAs/(Al,Ga)As multiple-quantum-well laser diodes and their influence on the kinks in output optical power are investigated. For the investigation, self-consistent electro-thermal-optical simulation and measurement of fabricated devices are used. From this investigation, the optimal P-cladding thickness that provides single-lateral-mode operation is determined, so that high beam quality can be achieved even at high output powers.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.3
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• pp.258-264
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• 2004

In this paper, MMIC double balanced star mixer for 40 ㎓ was implemented on GaAs substrate with backside vias. In the design of the MMIC mixer, the design of balun and diode was required. A novel balun structure using microstrip to CPS was presented. The 40 ㎓ balun was designed based on the design experience of the scale-down balun by 2 ㎓. The balun may be suitable for fabrication in MMIC process with backside via and can easily be applied for DBM(Double Balanced Mixer). A Schottky diode was designed and implemented using p-HEMT process considering the compatability with other high frequency MMIC's fabricated on p-HEMT base process. Finally, the double balanced star mixer was fabricated using the balun and the p=HEMP Schottky diode. The measured performance of mixer shows 30 ㏈ conversion loss at 18 ㏈m LO power. This insufficient performance is caused by the unwanted diode at AlGaAs junction in vertical structure of p-HEMT. If the p-HEMT's gate is recessed to AlGaAs layer, and so the diode is eliminated, the mixer's performances will be improved.