(Al/sub 0.5/Ga/sub 0.5/)/sub 0.65/In/sub 0.35/P/Ga/sub 0.65/In/sub 0.35/P double-heterostructure orange light-emitting diodes

Visible light-emitting diodes (LEDs) emitting at 615 nm and employing the AlGaInP/GaInP double heterostructure (DH) grown on a lattice-matched GaAs/sub 0.7/P/sub 0.3/ substrate have been fabricated for the first. The external quantum efficiency of 0.156% for the orange LEDs can be achieved by introducing the GaP material as the current spreader and window layer for the DH LEDs.<>     

GaInP气相外延中Si的掺杂行为及发光二极管材料的制备

用MOCVD方法生长GaInP及其掺杂材料，并对Si的掺杂行为进行了较详细的研究。采用低温度冲层技术可有效地控制高温（＞700℃）生长GaInP及其掺杂材料的组分，从而使得GaInP掺Si的电子浓度达8×1018cm－3。在此基础上，进行了GaInP发光二极管材料的生长，所得器件具有良好的I－V曲线。     

隧道结AlGaInP发光二极管

报道了通过隧道结将衬底的导电类型从n型转变到p型,从而可以利用n型GaP作为以n型GaAs为衬底的AlGaInP发光二极管的电流扩展层.n型电流扩展层的电阻率低于p型电流扩展层的电阻率,这种结构改善了电流扩展层的作用,从而提高了发光二极管的光提取效率.对3μm GaP电流扩展层的发光二极管,实验结果表明,隧道结发光二极管的发光功率与具有相同基本结构的传统发光二极管相比,20mA时发光功率提高了50%,100mA时提高了66.7%.     

隧道结AlGaInP发光二极管

报道了通过隧道结将衬底的导电类型从n型转变到p型,从而可以利用n型GaP作为以n型GaAs为衬底的AlGaInP发光二极管的电流扩展层.n型电流扩展层的电阻率低于p型电流扩展层的电阻率,这种结构改善了电流扩展层的作用,从而提高了发光二极管的光提取效率.对3μm GaP电流扩展层的发光二极管,实验结果表明,隧道结发光二极管的发光功率与具有相同基本结构的传统发光二极管相比,20mA时发光功率提高了50%,100mA时提高了66.7%.     

GaInAsP过渡层在808 nm GaAsP/(Al)GaInP半导体激光器中降电压的应用

利用金属有机化学气相沉积的方法在GaAs衬底上生长了GaInAsP外延层及GaAsP/(Al)GaInP激光器外延层。生长的GaInAsP外延层与GaAs晶格匹配,并且带隙处于Ga_0.5In_0.5P与GaAs中间。在GaInP/GaAs异质结界面插入此结构的GaInAsP过渡层,可以有效的降低异质结的带阶,尤其是价带带阶。相比于突变GaInP/GaAs异质结的808 nm GaAsP/(Al)GaInP半导体激光器,含有GaInAsP过渡层的半导体激光器具有更低的工作电压。因此,在350 mW输出功率下,半导体激光器的功率转换效率由52%提高至60%。并且在大电流注入下,含有GaInAsP过渡层的半导体激光器由于产生的焦耳热减少,具有更高的输出功率。     

Initial stages of InP/GaP (100) and (111)A,B grown by metal organic chemical vapor deposition

The initial stages of the three-dimensional metal organic vapor phase epitaxy growth of InP/GaP (100) and (111)_A,B were studied by atomic force microscopy (AFM) and Rutherford back scattering (RBS). We have shown that the heteroepitaxial growth takes place under Stranski–Krastanov mode (layer by layer and dislocation free island growth). By combining RBS and AFM results, we show that the wetting layer is about 0.51 and 0.4 nm for (100) and (111)_A,B orientated substrates, respectively. The critical thickness is found to depend on the substrate orientation. However, we show by the AFM technique that the shape, the height and the size of uncapped InP/GaP self-organized nanostructures depend on the amount of InP deposited and on the substrate orientation. In particular, the structure grown on (111)_A,B substrate presents higher islands than the structure grown on (100). Therefore, the formation of nanostructures on substrates different from (100) is an interesting possibility to be investigated.     

A high brightness GaP multicolor LED

A multicolor LED which can emit red, green, and any other colored light between red and green, such as orange and yellow, has been developed. This new LED is fabricated by growing epitaxially a double junction of red and green light emission on one side of a GaP substrate. The four epitaxial layers of GaP, referred to as n1, p1, p2, and n2, are grown by liquid phase epitaxy on the     

Improved Extraction Efficiency of Light-Emitting Diodes by Modifying Surface Roughness With Anodic Aluminum Oxide Film

An anodic alumina oxide (AAO) film with nano-roughening is added on the top window layer of AlGaInP light-emitting diodes (LEDs) to improve the light extraction of the device. The AAO film has a natural porosity to provide light scattering centers at the surface, allowing an increase of light emission intensity with no loss of or damage to the semiconductor material. Further, the fabricated AAO film with a refractive index is about which is intermediate between those of air and the window layer of GaP. By inserting this layer between the ambient and GaP, it broadens the critical angle for light emission and reduces internal reflection. Experiments with laboratory-fabricated AlGaInP devices of conventional design demonstrated a 32% improvement in the luminous intensity at 20 mA for the device with the AAO layer. This letter shows by theory and experiment that AAO films can be used as a low-cost, easily implemented surface nano-roughening for improving extraction efficiency of AlGaInP LEDs.     

Epitaxial GaP by a semi-sealed dip process for high efficiency red LED's

A semi-sealed dip process has been used to grow Zn-O doped GaP layers for high efficiency red LED's. A close fitting floating quartz plug is used to prevent volatilization of Zn, Ga₂O, and GaP during saturation. Double epitaxial layers with efficiencies as high as 8. 0% have been grown by this process.     

Properties of GaP light-emitting diodes grown on spinel substrates

Red and green GaP electroluminescent diodes have been successfully fabricated from GaP grown heteroepitaxially on spinel substrates by a vapor phase/liquid phase two-stage process. Current-voltage and light emission characteristics of the diodes are compared with those grown on bulk substrates. Quantum efficiencies up to 0·1 per cent in the red and 0·01 per cent in the green have been obtained.     

分子束外延生长的GaAs/GaInP双结电池研究

We report the recent result of GaAs/GaInP dual-junction solar cells grown by all solid-state molecularbeamepitaxy(MBE).The device structure consists of a GaIn0.48P homojunction grown epitaxially upon a GaAs homojunction,with an interconnected GaAs tunnel junction.A photovoltaic conversion efficiency of 27% under the AM1.5 globe light intensity is realized for a GaAs/GaInP dual-junction solar cell,while the efficiencies of 26% and 16.6% are reached for a GaAs bottom cell and a GaInP top cell,respectively.The energy loss mechanism of our GaAs/GaInP tandem dual-junction solar cells is discussed.It is demonstrated that the MBE-grown phosphide-containing Ⅲ–V compound semiconductor solar cell is very promising for achieving high energy conversion efficiency.     

InP quantum dots in (1 0 0) GaP: Growth and luminescence

We describe the growth and optical emission from strained InP quantum wells and quantum dots grown on GaP substrates using gas-source molecular beam epitaxy. Self-organized quantum dot formation takes place for InP coverage greater than 1.8 monolayers on the (1 0 0) GaP surface. Atomic force and scanning-electron microscopy studies indicate that unburied dots have a lateral size of 60–100 nm and are about 20 nm high, with dot densities in the range of 2–6×10⁸ cm⁻² for InP coverage between 1.9 and 5.8 MLs. Intense photoluminescence is emitted from both the quantum wells and the quantum dots at energies of about 2.2 and 2.0 eV, respectively. Time-resolved measurements indicate rather long carrier lifetimes of about 19 ns in the quantum wells and about 3 ns in the quantum dots. The data indicate that the InP/GaP quantum wells form a type-II band system, with electrons in the X valleys of the GaP recombine with holes in the InP. Furthermore, in the InP/GaP quantum dot system, the conduction band edge in the X valley of the GaP is nearly aligned with that in the Γ valley of the InP. Rapid thermal annealing of the quantum dots results in at least a six-fold enhancement of integrated emission intensity as well as some Ga-In interdiffusion. The low interdiffusion activation energy indicates that the material near the interface between the GaP matrix and the InP dots is not free of defects.     

The growth and properties of high performance AlGalnP emitters using a lattice mismatched GaP window layer

The growth and properties of high performance surface light emitting diodes which utilize a GaP window layer are presented. The devices consist of an AlGaInP double heterostructure lattice matched to a GaAs substrate. A lattice mismatched GaP layer is then grown on top of the heterostructure. The resulting upper confining and window layers have high electrical conductivity and optical transmissivity allowing for the fabrication of red-orange and yellow emitters with performance superior to existing commercial technologies. The effect of different confining and window layer structures on device performance is described, including characteristics of the shortest wavelength AlGaInP green emitters yet reported.     

ZnO纳米岛的MOCVD自组装生长

利用低压金属有机源气相沉积 (L P- MOCVD)技术 ,在 (0 0 0 1 )蓝宝石衬底上生长 Zn O纳米岛 ,发现在适当的生长条件下 ,可以生长出规则排列的纳米岛 .实验发现随着生长时间的增加 ,在蓝宝石衬底上沉积的 Zn O晶体颗粒无论是密度还是体积都在增加 ,并出现颗粒之间的交叠现象 .与厚膜材料相比 ,相应的室温 PL 谱上显示出带边蓝移现象 ,随着生长温度的提高将大大增加 Zn O在蓝宝石衬底上成核的困难 .另外 ,所有样品的室温 PL 谱在带边附近均存在一个展宽峰 ,这可能是由表面态或晶体缺陷造成的 .研究表明选择合适的生长时间与生长温度是利用MOCVD生长高质     

Investigation of GaNxP1−x/GaP LED structure optical properties

GaN_xP_1−x alloy represents a novel compound semiconductor that has attracted considerable interest as a candidate for realization of light emitting diodes (LEDs) in the green-red range of the visible spectra. Simple GaN_xP_1−x/GaP LED structures grown by low-preassure metalorganic vapor phase epitaxy and containing different N contents (0.6–2.3%) were investigated. The hierarchy of N complexes that generate different bound states were determined from photocurrent and electroluminescence spectra for different N concentrations in the GaN_xP_1−x layer. From the experimental measurements, it was confirmed that the electroluminescence emission peaks show discrete emission maxima at ∼608 nm and ∼628 nm with increasing N content due to formation of N clusters.     

The causes of emitting-power instability in GaP:N LED

A complex study of injection-enhanced processes in GaP:N light emitting diodes under forward bias (I = 5–30 mA) during the first 2–5 min has been carried out. The electrical, electroluminescent methods, DLTS technique and the method of secondary emission mass spectroscopy have been used. It has been shown that the instability of luminous power of GaP:N LEDs is associated with recombination-enhanced annealing defects in the active region of devices, rather than processes at the contacts. It has been found, that stable LEDs have a significantly higher concentration of O, C and their compounds.A reliable physical model of the processes involved is proposed.     

生长在GaSb_xP_（1－x）（001）衬底上GaP的能带结构

采用半经验紧束缚近似方法对生长在ＧａＳｂｘＰ１－ｘ（００１）衬底上ＧａＰ的电子能带结构进行计算。ＧａＰ为间接能隙型的半导体，计算表明，当衬底中Ｓｂ组分ｘ≥０．５７时，应变的ＧａＰ薄层由间接能隙变成直接能隙的半导体。因应变，ＧａＰ原来简并的最低Ｘ点导带能级及价带顶（Γ点）能级发生分裂。随着Ｘ增大，分裂值变大。文中最后计算了价带能级到导带底跃迁的振子强度，对发光效率作了讨论。     

Optical techniques useful for characterizing GaP crystals (review article)

Several optical techniques useful for characterizing GaP LPE crystals grown for light emitting diode applications will be described. The non-exhaustive discussion is primarily in the context of diagnostics developed in studies of the near bandedge emission and the minority carrier lifetime in GaP in the temperature range 100°-300°K. Optical absorption and transient and steady state photoluminescence measurements performed with photon counting techniques are emphasized. The diagnostics described provide many of the parameters pertinent to the luminescent quality of GaP crystals.     

High-performance 670-nm AlGaInP/GaInP visible strained quantum welllasers

We have grown high-performance AlGaInP/GaInP visible (670 mn) strained quantum well lasers by low-pressure metalorganic chemical vapor deposition. With AlInP cladding layer, a high-power AlGaInP/GaInP visible laser diode is achieved. Its threshold current is about 30 mA. The output power of this laser diode can maintain, at least, at 32 mW under continuous-wave (CW) operation at room temperature. High slope efficiency (0.8 mW/mA) and differential quantum efficiency (0.87) can be achieved. To improve beam quality, AlGaInP/GaInP visible lasers with and without depressed index cladding layer are theoretically and experimentally studied. From experimental results, the transverse beam divergence can be reduced from 41.4° to 26.2° while maintaining a low threshold current (from 36 mA to 46 mA). By using the transfer matrix method, our theoretical calculations are in good agreement with the experimental results     

Ultra-wide electroluminescence spectrum of LED heterostructures based on GaPAsN semiconductor alloys

In this paper, we present the results of the white light-emitting diodes (LEDs) construction based on GaPAsN semiconductor alloys on a GaP substrate. Heterostructure electroluminescence with a continuous emission spectrum in the range from 350 nm to 1050 nm is observed. The output of light through the side walls and the face side of the sample enabled us to achieve white light emission by means of ultra-wide electroluminescence spectrum covering all visible spectrum and part of the near IR spectral range. While extracting emission through substrate, the short-wavelength part of the visible spectra is absorbed at GaP layer.