The coupling interaction between an individual optical emitter and the propagating surface plasmon polaritons in a graphene microribbon(GMR) waveguide is investigated by numerical calculations, where the emitter is situated above the GMR or in the same plane of the GMR. The results reveal a multimode coupling mechanism for the strong interaction between the emitter and the propagating plasmonic waves in graphene. When the emitter is situated in the same plane of the GMR, the decay rate from the emitter to the surface plasmon polaritons increases more than 10 times compared with that in the case with the emitter above the GMR.
利用模拟软件研究施主表面态特性与AlGaN/GaN异质结构中二维电子气(2dimensional electron gas,2DEG)形成之间的关系,分析施主表面态电离过程以及表面态能级位置、表面态密度的影响。结果表明:施主表面态为2DEG的电子来源;AlGaN能带分布及2DEG密度随AlGaN厚度、施主表面态能级位置、施主表面态密度的改变而改变。
The effect of silver nanostructures prepared by nanosphere lithography on the photoluminescence(PL) properties of blue-emitting In Ga N/Ga N quantum wells(QWs) is studied. Arrays of silver nanoparticles are fabricated to yield a collective surface plasmonic resonance(SPR) near to the QWs emission wavelength. A large enhancement in peak PL intensity is observed, when the induced SPR wavelength of the nanoparticles on the QWs sample matches the QWs emission wavelength. The study proves that the SPRs could enhance the light emission efficiency of semiconductor material.
The electrical properties of the structure of GaN grown on an Si (111) substrate with low-temperature (LT) AlN interlayers by metal-organic chemical-vapour deposition are investigated. An abnormal P-type conduction is observed in our GaN-on-Si structure by Hall effect measurement, which is mainly due to the Al atom diffusing into the Si substrate and acting as an acceptor dopant. Meanwhile, a constant n-type conduction channel is observed in LT-AlN, which causes a conduction-type conversion at low temperature (50 K) and may further influence the electrical behavior of this structure.
Group Ⅲ-nitride material system possesses some unique properties,such as large spectrum coverage from infrared to deep ultraviolet,wide energy band gap,high electron saturation velocity,high electrical breakdown field,and strong polarization effect,which enables the big family has a very wide application range from optoelectronic to power electronic area.Furthermore,the successful growth of GaN-related III-nitride material on large size silicon substrate enable the above applications easily realize the commercialization,because of the cost-effective device fabrication on the platform of Si-based integrated circuits.In this article,the progress and development of the GaN-based materials and light-emitting diodes grown on Si substrate were summarized,in which some key issues regarding to the material growth and device fabrication were reviewed.
We demonstrate the fabrication of hexagonal nano-pillar arrays at the surface of GaN-based light-emitting diodes (LEDs) by nanosphere lithography. By varying the oxygen plasma etching time, we could tune the size and shape of the pillar. The nano-pillar has a truncated cone shape. The nano-pillar array serves as a gradual effective refractive index matcher, which reduces the reflection and increases light cone. It is found that the patterned surface absorbs more pumping light. To compare extraction efficiencies of LEDs, it is necessary to normalize the photoluminescence power spectrum with total absorption rate under fixed pumping power, then we could obtain the correct enhancement factor of the photoluminescence extraction efficiency and optimized structure. The highest enhancement factor of the extraction efficiency is 10.6.
There are two kinds of recurrence relations for the spherical functions Pml. The first are those with the same m but different l. Thesecond are those with the same l but different m. The spheroidal functions are extensions of the spherical functions. Recurrencerelations of the first kind are obtained for the spheroidal functions in recent studies. Using the shape invariance method in super-symmetric quantum mechanics, we investigate the second type of recurrence relations for the spheroidal functions. The resultsshow that the second kind of recurrence relation can not be extended to the spheroidal functions.
