硒化鋅及其三元,四元化合物之光學性質研究

Abstract

本論文係利用光激螢光譜,反射光譜及拉曼光譜,來研究硒化鋅及 其三元,四元化合物之光學特性. 實驗結果可分為三部份:一 研究 由分子磊晶法所成長之硒化錳鋅磊晶之光學特性,並比較由高週波濺鍍法 所成長之硒化錳鋅薄膜之光學特性差異.硒化錳鋅磊晶之半導體能階與錳 濃度大致成正比線性關係;晶格振動模式應為混合態模式;由光激螢光譜, 拉曼光譜可間接得知由晶格錯位所造成之應變效應與厚度關係;藉由比較 LO聲子之對稱性及強度可比較樣品品質之好壞.二 研究與硒化鉻鋅/硒化 鋅結構有關之多層量子井變溫光激螢光譜.研究發現,利用寬能帶四元化合 物硒硫化鎂鋅作為緩衝層或增加量子井的數目,對於加強發光效率都有幫 助.並且分析發光譜線發現,兩者之發光機制不同,因此所發螢光可在視覺 上造成不同的效果.三 研究硒化錳鋅及銻化鋅磊晶之變溫半導體能階.在 此利用簡單三參數方程式來找尋能階與溫度的最佳關係.此方程式不但比 一般常用之方程式更能符合實驗數據,並且也滿足在理論上聲子與電子交 互作用的假設. The optical properties of ZnSe based ternary and quaternarycompounds were invertigated by using photoluminescence (PL), reflection,and Raman spectroscopy methods. Two of ZnSe based compounds, ZnMnSeepilayers which were grown on GaAs (100) by molecular beam epitaxy (MBE)technique and ZnMnSe thin films which were grown on thin glasses byradio frequency (RF) sputtering techniuqe, were studied. Photoluminescenceand reflection measurements manifest that the energy gap increasinglinearly with Mn concentration x. Raman scattering spectroscopy of ZnMnSeepilayers and ZnMnSe thin films exhibits mixed-mode behaviors. PL and Raman spectra manifest the stress effect due to lattice mismatch wasreleased for the films with thickness larger than 1000 A. The crystalqualities can be justified by comparing the symmetry and intensity ofthe LO phonon peaks. Temperature dependence of photoluminescence spectroscopy of ZnCdSe/ZnSe based multi-quantum-well structure epilayers was also investigated. The luminescence efficiency was found to be improvedby using a wider band-gap quaternary alloy ZnMgSSe as buffer layers.The luminescence efficiency can be also improved by increasing the layers of quantum wells. The mechanism of the enhancement of the luminescence intensities for the above mentioned methods might be very different. A three-parameter simple equation was used to fit thetemperature dependence of ZnMnSe and ZnTe epilayer semiconductorband gaps. Our formula is justified both in practical and theoretical grounds. This is because our formula is shown to be compatible with reasonable assumptions for the influence of phonons on the band-gapenergy. In addition to this, the fitting result is numberically betterthan that obtained by using the widely quoted-Varshni equation.Besides, we also intorduce the evolution of fitting energy equations and justify its validation.