• Title, Summary, Keyword: Quantum efficiency

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Relation Between Flat-band Voltage and Quantum Efficiency of InSb MWIR Detector (InSb 중적외선 검출기의 Flat-band 전압과 양자효율의 상관관계)

  • Kim, Young-Chul;Eom, JunHo;Jung, Han;Kim, SunHo;Kim, NamHwan;Kim, Young-Ho
    • Journal of the Semiconductor & Display Technology
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    • v.17 no.2
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    • pp.12-15
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    • 2018
  • InSb (III-V compound semiconductor) is used for photodiode to detect the mid-wavelength infrared radiation. Generally the quantum efficiency of InSb IR FPAs(Focal Plane Arrays) is known to be determined by thickness of InSb and transmittance of anti-reflection coating layer. In this study, we confirmed that the C-V characteristics of detector array affects the quantum efficiency of the InSb IR FPAs. We fabricated the IR FPAs with various $V_{fb}$(flat band voltage) values and confirmed the tendency between the $V_{fb}$ value and quantum efficiency of the IR FPAs.

Measurement of the Radiative Quantum Efficiency of a Solid-State Laser Using Photoacoustic Spectroscopy (광음향 분광을 이용한 고체레이저의 방사양자효율 측정)

  • Kim, Byung-Tai
    • Korean Journal of Optics and Photonics
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    • v.26 no.2
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    • pp.98-102
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    • 2015
  • The radiative quantum efficiency of a solid-state laser was measured by photoacoustic spectroscopy with a PZT as the detector. The radiative quantum efficiency was about 58.3 % for a laser-diode pumped Nd:S-VAP laser under lasing conditions. The measurement of radiative quantum efficiency was presented as an effective method for the optimization of a laser resonator.

Calculation of the Quantum Efficiency of Phosphor Screens in CRTs and FL Tubes

  • Ozawa, Lyuji;Tian, Yakui
    • Journal of Information Display
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    • v.11 no.3
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    • pp.128-133
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    • 2010
  • The quantum efficiencies of CRT and FL tubes that use a phosphor screen as transducer of invisible particles to light in visible spectrum wavelengths were calculated in this study. The phosphor screens in CRT tubes have quantum efficiencies greater than 3,000, which give the luminance of comfortable images on phosphor devices for the observation by the eyes. The established FL tubes have the amazing quantum efficiency of $3{\times}10^{10}$ photons per moving electron per FL tube, which allows the illumination of a $5{\times}5\;m^2$ room by three FL tubes, with heating at $40^{\circ}C$. Thus, FL tubes, including for backlighting of LCD displays, have a superior over other illumination sources.

Improvement in LED structure for enhanced light-emission

  • Park, Seong-Ju
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.21-21
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    • 2003
  • To increase the light-emission efficiency of LED, we increased the internal and external quantum efficiency by suppressing the defect formation in the quantum well and by increasing the light extraction efficiency in LED, respectively. First, the internal quantum efficiency was improved by investigating the effect of a low temperature (LT) grown p-GaN layer on the In$\sub$0.25/GaN/GaN MQW in green LED. The properties of p-GaN was optimized at a low growth temperature of 900oC. A green LED using the optimized LT p-type GaN clearly showed the elimination of blue-shift which is originated by the MQW damage due to the high temperature growth process. This result was attributed to the suppression of indium inter-diffusion in MQW layer as evidenced by XRD and HR-TEM analysis. Secondly, we improved the light-extraction efficiency of LED. In spite of high internal quantum efficiency of GaN-based LED, the external quantum efficiency is still low due to the total internal reflection of the light at the semiconductor-air interface. To improve the probability of escaping the photons outside from the LED structure, we fabricated nano-sized cavities on a p-GaN surface utilizing Pt self-assembled metal clusters as an etch mask. Electroluminescence measurement showed that the relative optical output power was increased up to 80% compared to that of LED without nano-sized cavities. I-V measurement also showed that the electrical performance was improved. The enhanced LED performance was attributed to the enhancement of light escaping probability and the decrease of resistance due to the increase in contact area.

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유기 발광 다이오드의 광 추출 효율 개선을 위한 다양한 광학기능구조의 적용

  • Kim, Yang-Du;Kim, Gwan;Heo, Dae-Hong;Lee, Heon
    • Ceramist
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    • v.21 no.1
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    • pp.64-79
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    • 2018
  • Recent years, OLEDs have been progressed intensively and been widely applied to Display and Lighting industry,Almost 100% internal quantum efficiency was achieved by developing new materials and structure optimization. However, external quantum efficiency was still low due to total internal reflection of light inside OLED devices and absorption of light at the surface of metal electrode. In order to improve external quantum efficiency of OLED devices, various kinds of optical functional structures were introduced to inside and outside of OLED devices to increase light extraction efficiency. In this paper, various efforts to apply optical functional structures in OLED devices were reviewed and way to improve light extraction efficency of OLED devices were discussed.

Enhanced Internal Quantum Efficiency and Light Extraction Efficiency of Light-emitting Diodes with Air-gap Photonic Crystal Structure Formed by Tungsten Nano-mask

  • Cho, Chu-Young;Hong, Sang-Hyun;Kim, Ki Seok;Jung, Gun-Young;Park, Seong-Ju
    • Bulletin of the Korean Chemical Society
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    • v.35 no.3
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    • pp.705-708
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    • 2014
  • We demonstrate the blue InGaN/GaN multiple quantum wells light-emitting diodes (LEDs) with an embedded air-gap photonic crystal (PC) which was fabricated by the lateral epitaxial overgrowth of GaN layer on the tungsten (W) nano-masks. The periodic air-gap PC was formed by the chemical reaction of hydrogen with GaN on the W nano-mask. The optical output power of LEDs with an air-gap PC was increased by 26% compared to LEDs without an air-gap PC. The enhanced optical output power was attributed to the improvement in internal quantum efficiency and light extraction efficiency by the air-gap PC embedded in GaN layer.

Modeling and simulation of efficiency droop in GaN-based blue light-emitting diodes incorporating the effect of reduced active volume of InGaN quantum wells

  • Ryu, Han-Youl;Ryu, Guen-Hwan;Choi, Young-Hwan;Ma, Byungjin
    • Current Applied Physics
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    • v.17 no.10
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    • pp.1298-1302
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    • 2017
  • The efficiency droop of InGaN-based blue light-emitting diodes (LEDs) is analyzed using numerical simulations with a modified ABC carrier recombination model. The ABC model is modified to include the effect of reduced effective active volume of InGaN quantum wells (QWs) and incorporated into the numerical simulation program. It is found that the droop of internal quantum efficiency (IQE) can be well explained by the effect of reduced light-emitting active volume without assuming a large Auger recombination coefficient. A simulated IQE curve with the modified ABC model is found to fit quite well with a measured efficiency curve of an InGaN LED sample when the effective active volume takes only 2.5% of the physical volume of QWs. The proposed numerical simulation model incorporating the reduced effective active volume can be advantageous for use in the modeling and simulation of InGaN LEDs for higher efficiency.

A Study on Improvement of the Light Emitting Efficiency on Flip Chip LED with Patterned Sapphire Substrate by the Optical Simulation (광학 시뮬레이션을 이용한 Patterned Sapphire Substrate에 따른 Flip Chip LED의 광 추출 효율 변화에 대한 연구)

  • Park, Hyun Jung;Lee, Dong Kyu;Kwak, Joon Seop
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.28 no.10
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    • pp.676-681
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    • 2015
  • Recently many studies being carried out to increase the light efficiency of LED. The external quantum efficiency of LED, generally the light efficiency, is determined by the internal quantum efficiency and the light extraction efficiency. The internal quantum efficiency of LED was already reached to more than 90%, but the light extraction efficiency is still insufficient compared with the internal quantum efficiency because the total internal reflection is generated in the interface between the LED chip and air. Thus, we studied about flip chip LED with PSS and performed the optical simulation which find more optimized PSS for flip chip LED to increase the light extraction efficiency. Decreasing of the total internal reflection and effect of diffused reflection according to PSS improved the light extraction efficiency. To get more higher the efficiency, we simulated flip chip with PSS that the parameters are arrangement, edge spacing, radius, height and shape of PSS.

The Design of Long-life and High-efficiency Passive LED Drivers using LC Parallel Resonance (LC 병렬공진을 이용한 고효율 장수명 LED 구동회로 설계)

  • Lee, Eun-Soo;Choi, Bo-Hwan;Cheon, Jun-Pil;Kim, Bong-Cheol;Rim, Chun-Taek
    • The Transactions of the Korean Institute of Power Electronics
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    • v.18 no.4
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    • pp.397-402
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    • 2013
  • This paper proposes a new passive type LED driver which satisfies the standard of power factor (PF) and total harmonic distortion (THD). The proposed passive LED driver also has high-efficiency and long-life time characteristics compared to active LED driver which is composed of op-amp, switches and so on. By using just passive components such as inductor, capacitor, and diode, it has resolved extremely short-life time and low-efficiency problems of previous LED drivers. It has achieved PF of 0.99, THD of 16.4 %, and the total efficiency of 95 %. The proposed passive LED driver is fully analyzed and verified by simulations and experiments, which results are in good agreement each other.