MOCVD生长InP/GaInAsP DBR结构及相关材料特性

Characterization of InP/GalnAsP DBRs Structures and Related Materials Grown by MOCVD

采用金属有机化学气相沉积(MOCVD)法InP衬底上成功地制备了GaxIn1-xAsyP1-y/InP交替生长的分布布喇格反射镜(DBR)结构以及与之相关的四元合金GaxIn1-xAsyP1-y和InP外延层。利用X射线衍射、扫描电子显微镜(SEM)、低温光致发光(PL)光谱等测量手段对材料的物理特性进行了表征。结果表明,在InP衬底上生长的InP外延层和四元合金GaxIn1-xAsyP1-y外延层77K光致发光(PL)谱线半峰全宽(FWHM)分别为9.3meV和32meV,说明形成DBRs结构的交替层均具有良好的光学质量。X射线衍射测量结果表明,四元合金GaxIn1-xAsyP1-y外延层与InP衬底之间的相对晶格失配仅为1×10-3。GaxIn1-xAsyP1-y/InP交替生长的DBR结构每层膜的光学厚度约为λ/4n(λ=1.55/μm)。根据多层膜增反原理计算得出当膜的周期数为23时,反射率可达90％。

High quality unintentionally doped InP, quaternary alloy GaxIn1-AsyP1-y epilayers and the distributed Bragg reflectors(DBRs) formed alternately with high and low refractive index semiconductor materials have been grown on InP substrates in an atmospheric or low pressure metal organic chemical vapor deposition system made up in our laboratory. The trimethylindium(TMIn), trimethylgallium (TMGa), arsine(AsH3) and phosphine(pH3) are as the source materials. The properties of the epilayers were investigated by measurement of X-ray diffraction, X-ray rocking curve, scanning electronic microscope, low-temperature photoluminescence spectra in detail. The results indicated that the GaxIn1-xAsyP1-y, quaternary alloys epilayers grown by LP-MOCVD have good lattice match to InP substrates. The lattice mismatch is only 1×10-3 between GaxIn1-xAsyP1-y epilayers and InP substrates. And we obtained the InP and GaxIn1-xAsyP1-y epilayers with better optical quality. The FWHM of PL spectrum of the GaxIn1-xAsyP1-y epilayers and InP epilayers were 32, 9.3meV, respectively. The results measured by SEM indicated that we successfully obtained high quality DBR structures. They are formed by laying down alternating layers of GaxIn1-xAsyP1-y and InP semiconductors materials with different refractive index. The optical thickness of each layer of alternating growth layers is λ/4n (0.1μm). λ is the center wavelength, n is the refractive index of each alternating growth layer. Although when the number of alternating layers is 23, the reflectivity of the DBRs layers will reach 90%, but more epilayer will increase the resistance of the device and raise the threshold current. So it is important to optimize a suitable number of layers.