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21.
Strain Effect on Photoluminescences from InGaN MQWs with Different Barriers Grown by MOCVD 下载免费PDF全文
InGaN/GaN MQWs, InGaN/AlGaN MQWs and InGaN/AlInGaN MQWs are grown on (0001) sapphire substrates by MOCVD. Membrane samples are fabricated by laser lift-off technology. The photoluminescence spec-ra of membranes show a blue shift of peak positions in InGaN/GaN MQWs, a red shift of peak positions in InGaN/AlGaN MQWs and no shift of peak positions in InGaN/AIlnGaN MQWs from those of samples with substrates. Different changes in Raman scattering spectra and HR-XRD (0002) profile of InGaN/AlInGaN MQWs, from those of InGaN/GaN MQWs and InGaN/AlGaN MQWs, are observed. The fact that the strain changes differently among InGaN MQWs with different barriers is confirmed. The AIlnGaN barrier could adjust the residual stress for the least strain-induced electric field in InGaN/AIlnGaN quantum wells. 相似文献
22.
通过利用阳极氧化铝的方法制备高度有序的光子晶体结构作为纳米压印模板,将大面积光子晶体图案转移到了样品表面,解决了国际上小尺寸光子晶体制备困难的问题。采用纳米压印的方法在AlGaN基样品表面上制备了290 nm的周期光子晶体结构,并将表面具有光子晶体结构的AlGaN基样品正面出光强度提高121%。偏振特性的实验结果表明六角排列的孔状光子晶体将原来朝向样品侧面传播的TE偏振光偏折转向正面,从而增加光抽取效率,改变出光偏振度。指出远场角分辨图案的变化归因于光子晶体对出光的衍射和Bragg散射效果。实验中采用的创新性工艺可以用来制备具有高出光效率的深紫外发光二极管。 相似文献
23.
用正向电压法、管脚法和蓝白比法等三种方法测量GaN基白光LED的结温,获得了较为准确的结温,误差可以控制在4℃以内.正向电压法在恒定电流的条件下,得到了正向电压与结温的线性关系;蓝白比法在不同环境温度和不同注入电流两种情况下,都得到了蓝白比与结温较好的线性关系.提出了蓝白比法可能的物理机制,提高环境温度和增大注入电流都会使结温升高,蓝光峰值波长也会改变,这两个因素都会影响荧光粉的激发和发光效率.降低结温需要考虑的主要因素有白光LED的接触电阻、串联电阻和外量子效率,封装材料的热导率,反射杯和管脚的设计,以及空气散热部分的散热面积等. 相似文献
24.
本文报导了一种测量光耦合效率η的新实验方法。这个方法是建立于p-n结短路光电流原理上的。本文推导出适合于行波激光放大器的光耦合效率的公式。短路光电流用一检流计测量,利用公式获得光耦合效率的实验值。利用实验所测光耦合效率,测量了行波激光放大器的增益随注入电流变化的规律,其结果和实验符合。另外本文还介绍了在脉冲注入电流条件下测行波半导体激光放大器增益的实验方法。 相似文献
25.
Thin tungsten nitride (WNx) films were produced by reactive DC magnetron sputtering of tungsten in an Ar-N2 gas mixture. The films were used as Schottky contacts on AlGaN/GaN heterostructures. The Schottky behaviours of WNx contact was investigated under various annealing conditions by current-voltage (I-V ) measurements. The results show that the gate leakage current was reduced to 10-6 A/cm2 when the N2 flow is 400 mL/min. The results also show that the WNx contact improved the thermal stability of Schottky contacts. Finally, the current transport mechanism in WNx/AlGaN/GaN Schottky diodes has been investigated by means of I-V characterisation technique at various temperatures between 300 K and 523 K. A TE model with a Gaussian distribution of Schottky barrier heights (SBHs) is thought to be responsible for the electrical behaviour at temperatures lower than 523 K. 相似文献
26.
Strain effects on the polarized optical properties of InGaN with different In compositions 下载免费PDF全文
Strain effects on the polarized optical properties of c-plane and
m-plane Inx1-xN were discussed for different In
compositions (x=0, 0.05, 0.10, 0.15) by analyzing the relative
oscillator strength (ROS) and energy level splitting of the three
transitions related to the top three valence bands (VBs). The ROS
was calculated by applying the effective-mass Hamiltonian based on
k. p perturbation theory. For c-plane
InxGa1-xN, it was found that the ROS of | X >
and | Y >-like states were superposed with each
other. Especially, under compressive strain, they dominated in the
top VB whose energy level also went up with strain, while the ROS of the
| Z >-like state decreased in the second band.
For m-plane InxGa1-xN under compressive strain, the top
three VBs were dominated by | X >, | Z
>, and | Y >-like states,
respectively, which led to nearly linearly-polarized light
emissions. For the top VB, ROS difference between | X
> and | Z >-like states became
larger with compressive strain.
It was also found that such tendencies were more evident in layers
with higher In compositions. As a result, there would be more TE modes
in total emissions from both c-plane and m-plane InGaN with compressive
strain and In content, leading to a larger polarization degree.
Experimental results of luminescence from InGaN/GaN quantum
wells (QWs) showed good coincidence with our calculations. 相似文献
27.
Optimization of a solar-blind and middle infrared two-colour photodetector using GaN-based bulk material and quantum wells 下载免费PDF全文
This paper calculates the wavelengths of the interband
transitions as a function of the Al mole fraction of AlxGa1-xN bulk material. It is finds that when the Al mole fraction is
between 0.456 and 0.639, the wavelengths correspond to the solar-blind
(250~nm to 280~nm). The influence of the structure parameters of
AlyGa1-yN/GaN quantum wells on the wavelength and absorption
coefficient of intersubband transitions has been investigated by
solving the Schr?dinger and Poisson equations self-consistently. The
Al mole fraction of the AlyGa1-yN barrier changes from
0.30 to 0.46, meanwhile the width of the well changes from 2.9~nm to
2.2~nm, for maximal intersubband absorption in the window of the air
(3~μm <λ <5~μm). The absorption coefficient of the
intersubband transition between the ground state and the first
excited state decreases with the increase of the wavelength. The
results are finally used to discuss the prospects of GaN-based bulk
material and quantum wells for a solar-blind and middle infrared
two-colour photodetector. 相似文献
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