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The effects of InGaN layer thickness on the performance of InGaN/GaN p-i-n solar cells

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chinese Physics B 2013年第6期22卷 666-669页

作者：李亮赵德刚江德生刘宗顺陈平吴亮亮乐伶聪王辉杨辉 State Key Laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences suzhou institute of Nano-tech and Nano-bionics Chinese Academy of Sciences

InGaN/GaN p-i-n solar cells, each with an undoped In0.12Ga0.88N absorption layer, are grown on c-plane sapphire substrates by metal-organic chemical vapor deposition. The effects of the thickness and dislocation density of the absorp- tion layer on the collection efficiency of InGaN-based solar cells are analyzed, and the experimental results demonstrate that the thickness of the InGaN layer and the dislocation density significantly affect the performance. An optimized InGaN- based solar cell with a peak external quantum efficiency of 57% at a wavelength of 371 nm is reported. The full width at half maximum of the rocking curve of the （0002） InGaN layer is 180 arcsec.

关键词： nitride materials crystal growth solar cell X-ray diffraction

Time delay in InGaN multiple quantum well laser diodes at room temperature

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chinese Physics B 2010年第12期19卷 305-309页

作者：季莲江德生张书明刘宗顺曾畅赵德刚朱建军王辉段俐宏杨辉 State Key Laboratory of Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences suzhou institute of Nano-tech and Nano-bionics Chinese Academy of Sciences

This paper reports that a long delay between the beginning of pumping current pulse and the onset of optical pulse is observed in InGaN laser diodes. The delay time decreases as the pumping current increases, and the speed of the delay time reduction becomes slower as the current amplitude increases further. Such delay phenomena are remarkably less serious in laser diodes grown on GaN substrate than those on sapphire. It attributes the delay to the traps which cause a large optical loss by saturable absorption and retard the laser action. The traps can be bleached by capturing injected carriers. The effect of GaAs laser irradiation on InGaN laser action demonstrates that the traps responsible for the delay are deep centres which can be filled by the photo-assisted processes.

关键词： InGaN laser diode delay effect saturable absorber traps

GaN-based violet laser diodes grown on free-standing GaN substrate

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chinese Physics B 2009年第12期18卷 5350-5353页

作者：张立群张书明江德生王辉朱建军赵德刚刘宗顺杨辉 State Key Laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences suzhou institute of Nano-tech and Nano-bionics Chinese Academy of Sciences

A violet laser diode （LD） structure is grown on a free-standing c-plane GaN substrate and 4 μm×800μm ridge waveguide LDs are fabricated. The electrical and the optical characteristics of LDs under different facet-coating and chip-mounting conditions are investigated under pulse mode operation. The active region temperatures of p-side up and p-side down mounted LDs are calculated with different injection currents. The calculated thermal resistances of p-side up and p-side down mounted LDs are 4.6 K/W and 3 K/W, respectively. The threshold current of the p-side down mounted LD is much lower than that of the p-side up mounted LD. The blue shift of the emission wavelength with increasing injection current is observed only for the LD with p-side down mounting configuration, due to the more efficient heat dissipation.

关键词： GaN laser diode mounting configuration active region temperature

Luminescence mechanism and energy level structure of Eu-doped GaN powders investigated by cathodoluminescence spectroscopy

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Science China(Physics,Mechanics & Astronomy) 2014年第4期57卷 628-631页

作者： WANG XiaoDan ZENG XiongHui XU Ke MAO HongMin MA ChunLan Department of Physics Suzhou University of Science and Technology suzhou institute of Nano-tech and Nano-bionics Chinese Academy of Sciences

1.5at% Eu-doped GaN powders were prepared by a co-precipitation *** X-ray diffraction(XRD)results shows that there is only the wurtzite *** spectra were measured at room temperature and liquid nitrogen temperature,*** band-to-band luminescence of GaN was shifted from 373 nm to 368 nm with the temperature decreasing from room temperature to liquid nitrogen *** luminescence peaks at 537,557,579,590,597,614,653 and 701 nm are attributed to the Eu ions related transitions in the host of GaN powders and the peak positions were not influenced by the variation of *** the increase of accelerating voltage,the intensity of all luminescence peaks was *** strongest luminescence peak at 614 nm shows non-symmetrical shape and is composed of 612,615 and 621 nm through Lorentzian fitting,which indicates there are oxygen and nitrogen environments of the Eu3+ions in the Eu-doped GaN powders.

关键词： Eu GaN energy level spectrum

Effect of surface treatment of GaN based light emitting diode wafers on the leakage current of light emitting diode devices

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chinese Physics B 2010年第1期19卷 501-504页

作者：王良吉张书明朱继红朱建军赵德刚刘宗顺江德生王玉田杨辉 State Key Laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences suzhou institute of Nano-tech and Nano-bionics Chinese Academy of Sciences

To form low-resistance Ohmic contact to p-type GaN, InGaN/GaN multiple quantum well light emitting diode wafers are treated with boiled aqua regia prior to Ni/Au （5 nm/5 nm） film deposition. The surface morphology of wafers and the current voltage characteristics of fabricated light emitting diode devices are investigated. It is shown that surface treatment with boiled aqua regia could effectively remove oxide from the surface of the p-GaN layer, and reveal defect-pits whose density is almost the same as the screw dislocation density estimated by x-ray rocking curve measurement. It suggests that the metal atoms of the Ni/Au transparent electrode of light emitting diode devices may diffuse into the p-GaN layer along threading dislocation lines and form additional leakage current channels. Therefore, the surface treatment time with boiled aqua regia should not be too long so as to avoid the increase of threading dislocation-induced leakage current and the degradation of electrical properties of light emitting diodes.

关键词： GaN light emitting diode surface treatment leakage current

The effects of sapphire nitridation on GaN growth by metalorganic chemical vapour deposition

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chinese Physics B 2011年第12期20卷 400-403页

作者：乐伶聪赵德刚吴亮亮邓懿江德生朱建军刘宗顺王辉张书明张宝顺杨辉 State Key Laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences suzhou institute of Nano-tech and Nano-bionics Chinese Academy of Sciences

In situ optical reflectivity measurements are employed to monitor the GaN epilayer growth process above a lowtemperature GaN buffer layer on a c-plane sapphire substrate by metalorganic chemical vapour deposition. It is found that the lateral growth of the GaN islands and their coalescence are promoted in the initial growth stage if optimized nitridation time and temperature are selected when the substrate is pre-exposed to ammonia. As confirmed by atomic force microscopy observations, the quality of the CaN epilayers is closely dependent on the surface morphology of the nitridated buffer layer, especially grain size and nucleation density.

关键词： X-ray diffraction metalorganic chemical vapour deposition nitrides

Dependence of InGaN solar cell performance on polarization-induced electric field and carrier lifetime

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chinese Physics B 2013年第9期22卷 671-675页

作者：杨静赵德刚江德生刘宗顺陈平李亮吴亮亮乐伶聪李晓静何晓光王辉朱建军张书明张宝顺杨辉 State Key Laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences suzhou institute of Nano-tech and Nano-bionics Chinese Academy of Sciences

The effects of Mg-induced net acceptor doping concentration and carrier lifetime on the performance of a p-i-n InGaN solar cell are investigated. It is found that the electric field induced by spontaneous and piezoelectric polariza- tion in the i-region could be totally shielded when the Mg-induced net acceptor doping concentration is sufficiently high. The polarization-induced potential barriers are reduced and the short circuit current density is remarkably increased from 0.21 mA/cm2 to 0.95 mA/cm2 by elevating the Mg doping concentration. The carrier lifetime determined by defect density of i-InGaN also plays an important role in determining the photovoltaic properties of solar cell. The short circuit current density severely degrades, and the performance of InGaN solar cell becomes more sensitive to the polarization when carrier lifetime is lower than the transit time. This study demonstrates that the crystal quality of InGaN absorption layer is one of the most important challenges in realizing high efficiency InGaN solar cells.

关键词： nitride materials solar cell polarization

The Effects of a Low-Temperature GaN Interlayer on the Performance of InGaN/GaN Solar Cells

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chinese Physics Letters 2013年第2期30卷 247-249页

作者： LI Liang ZHAO De-Gang JIANG De-Sheng LIU Zong-Shun CHEN Ping WU Liang-Liang LE Ling-Cong WANG Hui YANG Hui State Key Laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of SciencesP.O.Box 912Beijing 100083 suzhou institute of Nano-tech and Nano-bionics Chinese Academy of SciencesSuzhou 215123

An InGaN/GaN p-i-n solar cell inserted with a 5-nm low-temperature(LT)GaN interlayer between the p-GaN cap layer and the InGaN i-layer is grown on a c-plane sapphire substrate by metal organic chemical vapor *** effects of the LT GaN interlayer on the performance of the InGaN/GaN solar cells are *** is found that the LT-GaN interlayer prevents the extension of threading dislocations from the InGaN layer to the p-GaN layer and improves the crystal quality of both the p-GaN cap layer and the InGaN i-layer,ultimately leading to an increasing external quantum efficiency and photocurrent density of the InGaN/GaN solar cells.

关键词： InGaN/GaN GaN sapphire

Growth condition optimization and mobility enhancement through prolonging the GaN nuclei coalescence process of AlGaN/AlN/GaN structure

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chinese Physics B 2015年第9期24卷 399-402页

作者：何晓光赵德刚江德生朱建军陈平刘宗顺乐伶聪杨静李晓静张书明杨辉 State Key Laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences suzhou institute of Nano-tech and Nano-bionics Chinese Academy of Sciences

AlGaN/AlN/GaN structures are grown by metalorganic vapor phase epitaxy on sapphire substrates. Influences of AlN interlayer thickness, AlGaN barrier thickness, and Al composition on the two-dimensional electron gas（2DEG） performance are investigated. Lowering the V/III ratio and enhancing the reactor pressure at the initial stage of the hightemperature GaN layer growth will prolong the GaN nuclei coalescence process and effectively improve the crystalline quality and the interface morphology, diminishing the interface roughness scattering and improving 2DEG mobility. AlGaN/AlN/GaN structure with 2DEG sheet density of 1.19 × 10^13cm^-2, electron mobility of 2101 cm^2·V^-1·s^-1, and square resistance of 249 Ω is obtained.

关键词： high electron mobility transistor two-dimensional electron gas GaN