一种基于AlGaN和石墨烯的紫外-红外双色探测器

通过MOCVD和CVD生长技术,利用高Al组分Al Ga N和单层石墨烯材料进行纵向集成,成功制备了日盲紫外-近红外双色探测器。在工作温度为室温、调制频率为209 Hz以及工作电压分别为10 V和5 V的工作条件下,所制备的双色探测器在紫外波段263 nm处的响应度为5.9 m A/W,在近红外波段1.15μm处的响应度为0.67 m A/W,并且探测器的响应度均随着工作电压的增加而增大。     

Effects of interface roughness on photoluminescence full width at half maximum in GaN/AlGaN quantum wells

Low temperature photoluminescence(PL) measurements have been performed for a set of GaN/AlxGa1-xN quantum wells(QWs). The experimental results show that the optical full width at half maximum(FWHM) increases relatively rapidly with increasing Al composition in the AlxGa1-xN barrier, and increases only slightly with increasing GaN well width. A model considering the interface roughness is used to interpret the experimental results. In the model, the FWHM’s broadening caused by the interface roughness is calculated based on the triangle potential well approximation. We find that the calculated results accord with the experimental results well.     

基于阿贝正弦条件的光子等频图和能带结构测试系统

通过结合电磁波在周期性纳米材料中的传播特性以及阿贝完备成像理论中的阿贝正弦条件,提出了一种快速测试光子等频图和能带结构的测试技术和光学检测系统。将无限筒长显微物镜作为一种把波矢空间直接转换到实空间的变换器件,并通过配备二维面阵CCD的光栅光谱仪实现了对周期性纳米材料的等频图和能带结构的一次性拍照,真正实现了方便、快速和无损的探测技术。利用自行搭建的测试系统对用自组装方法制备的二维周期性纳米材料进行了相关光学测试,通过实验测试结果和相关理论计算的对比验证了系统的可行性和可靠性,从而说明该光学系统在研究周期性纳米材料的光学特性方面具有一定的优势。     

Effects of polarization on intersubband transitions of Al_xGa_(1-x)N/GaN multi-quantum wells

The effects of polarization and related structural parameters on the intersubband transitions of AlGaN/GaN multiquantum wells (MQWs) have been investigated by solving the Schrdinger and the Poisson equations self-consistently. The results show that the intersubband absorption coefficient increases with increasing polarization while the transition wavelength decreases, which is not identical to the case of the interband transitions. Moreover, it suggests that the well width has a greater effect on the intersubband transitions than the barrier thickness, and the intersubband transition wavelength of the structure when doped in the barrier is shorter than that when doped in the well. It is found that the influences of the structural parameters differ for different electron subbands. The mechanisms responsible for these effects have been investigated in detail.     

间接耦合光电探测结构光致负阻效应的物理模型

系统地报道和探讨了在研究间接耦合光电探测结构光致负阻特性中所发现的一系列实验现象．在对这些实验现象综合分析的基础之上，提出了一种由一横向ＰＮＰＮ四重结构与一纵向ＮＰＮ管相互作用所产生的负阻效应的新模型．利用负阻峰域载流子特殊的输运机制，设计和研制出了上升、下降时间均为２ｎｓ左右，内部电流增益大于３０倍的硅光电探测单元器件．     

AlGaN基深紫外发光二极管研究进展

深紫外光源在杀菌消毒、生化检测、紫外固化、紫外通信等方面具有巨大的应用前景,基于AlGaN半导体的深紫外发光二极管(LED)因具有无毒、体积小、能耗低、寿命长、波长可调等优势,得到了广泛的关注和研究.经过近二十年的研究开发,AlGaN基深紫外LED无论是发光效率和器件寿命都得到了巨大的提升,已逐步开始商业化.然而,相对于GaN基蓝光LED,目前AlGaN基深紫外LED的效率仍旧非常低,还有很大的提升空间.本文首先介绍了深紫外LED的发展现状,并分析了导致器件效率低的原因.然后,分别从内量子效率、光提取效率以及电光转换效率三个方面对目前AlGaN基深紫外LED的研究状况进行了系统的回顾,总结了目前提高发光效率的各种手段和方法.最后对AlGaN基深紫外LED的未来发展进行了展望.     

Exciton–phonon interaction in Al_(0.4)Ga_(0.6)N/Al_(0.53)Ga_(0.47)N multiple quantum wells

The exciton-phonon interaction in Al_(0.4)Ga_(0.6)N/Al_(0.53)Ga_(0.47)N multiple quantum wells(MQWs) is studied by deepultraviolet time-integrated and time-resolved photoluminescence(PL).Up to four longitudinal-optical(LO) phonon replicas of exciton recombination are observed,indicating the strong coupling of excitons with LO phonons in the MQWs.Moreover,the exciton-phonon coupling strength in the MQWs is quantified by the Huang-Rhys factor,and it keeps almost constant in a temperature range from 10 K to 120 K.This result can be explained in terms of effects of fluctuations in the well thickness in the MQWs and the temperature on the exciton-phonon interaction.     

Effects of interface roughness on photoluminescence full width at half maximum in GaN/AIGaN quantum wells

Low temperature photoluminescence （PL） measurements have been performed for a set of GaN/AlxGal xN quantum wells （QWs）. The experimental results show that the optical full width at half maximum （FWHM） increases relatively rapidly with increasing A1 composition in the AlxGal xN barrier, and increases only slightly with increasing GaN well width. A model considering the interface roughness is used to interpret the experimental results. In the model, the FWHM＇s broadening caused by the interface roughness is calculated based on the triangle potential well approximation. We find that the calculated results accord with the experimental results well.     

Occurrence and elimination of in-plane misoriented crystals in AIN epUayers on sapphire via pre-treatment control

AlN epilayers are grown directly on sapphire （0001） substrates each of which has a low temperature AlN nucleation layer. The effects of pretreatments of sapphire snbstrates, including exposures to NH3/H2 and to H2 only ambients at different temperatures, before the growth of AlN epilayers is investigated. In-plane misoriented crystals occur in N-polar AlN epilayers each with pretreatment in a H2 only ambient, and are characterized by six 60°-apart peaks with splits in each peak in （1012） phi scan and two sets of hexagonal diffraction patterns taken along the [0001] zone axis in electron diffraction. These misoriented crystals can be eliminated in AlN epilayers by the pretreatment of sapphire substrates in the NH3/H2 ambient. AlN epilayers by the pretreatment of sapphire substrates in the NH3/H2 ambient are Al-polar. Our results show the pretreatments and the nucleation layers are responsible for the polarities of the AlN epilayers. We ascribe these results to the different strain relaxation mechanisms induced by the lattice mismatch of AlN and sapphire.