利用銅與鎵共摻雜的方式在電漿輔助式分子束磊晶系統中成長氧化鋅的磊晶層

P-type Behavior in Cu-Ga Codoped ZnO Epilayers Grown by Plasma-Assisted Molecular Beam Epitaxy

黃士榮(Hsi-Jung Huang)

指導教授 ： 楊祝壽

大同大學/電機資訊學院/光電工程研究所/碩士(2011年)

摘要

在本篇論文中，利用分子束磊晶法成長P型的的氧化鋅磊晶層，其成長方式是利用銅、鎵共摻雜法。藉由反射光譜、光激螢光譜、拉曼散射、X光繞射量測、掃描式電子顯微鏡、X光光電子能譜儀及霍爾量測等技術，探討磊晶層的結構與光學特性。在光激螢光光譜中發現，少量的銅摻雜會使得氧化鋅磊晶層本身的品質變好，原因來自於銅二價離子 (0.73 Ả) 與鋅的二價離子半徑 (0.74 Ả) 非常接近，當少量銅摻雜進入減少本質缺陷(例如:鋅空缺)，因此自由激子的放光變強，而且束縛激子螢光半寬也從 8.63 meV 變窄到 6.05 meV。在拉曼散射光譜中，氧化鋅聲子模態也因少量的銅摻雜而變明顯。藉由霍爾量測分析發現，磊晶層中電子濃度隨著銅摻入越多而減少(-5.0 ×1017 cm-3 ~ -4.3×1013 cm-3)，這是由於互補效應的結果。然而，其電性還是呈現ｎ型。藉由X光繞射量測的分析，發現銅在 1100oC 時候有氧化銅(立方結構)與氧化鋅(六角結構)共存的狀態，使得結晶品質大幅下降。所以我們改用銅、鎵共摻雜的方式製作P型氧化鋅，藉由鎵的進入，改善其電性以及結晶品質。最後我們成功地製作出p型氧化鋅磊晶層及其載子濃度為 5×1014 cm-3。
　　另一方面，我們使用醋酸鋅、醋酸鎂與碳酸氫鈉混和純水的方式，藉由微波加熱來製作氧化鋅以及氧化鎂鋅的奈米粉末。經微波加熱完畢後的白色粉末，藉由高溫鍛燒爐從 400oC 到 800oC 燒結處理8小時，來探討不同溫度對於粉末結晶品質的影響。研究過程發現，當燒結的溫度越高，氧化鋅奈米粉末的結晶就越好。在光激螢光譜中發現，氧化鋅近能隙放光的主要訊號(373 nm)隨半寬越來越窄。在製作氧化鎂鋅粉末過程中，藉由改變前驅物混合步驟的順序，使得已經趨飽和的氧化鎂鋅粉末，再提高其光子能量。

關鍵字

氧化銅鋅 ； 銅鎵共摻雜 ； 電漿輔助式分子束磊晶系統 ； 正型氧化鋅

並列摘要

In this work, we demonstrate the p-type ZnO epilayers with Cu-Ga co-doped method by using plasma-assisted molecular beam epitaxy (PA-MBE). It is difficult to fabricate the p-type ZnO by mono-doped Cu due to the extremely rare solid solubility of Cu and hardly controlled the valence number of Cu. The X-ray diffraction (XRD), photoluminescence, Raman scattering, and Hall measurement are employed to characterize the efficacy of co-doped Ga and Cu. In a few Cu content, i.e. lower Cu element flux, XRD and PL reveal the improved crystal quality due to similar ionic radius of Cu2+ (0.73 Ả) and Zn2+ (0.74 Ả). In PL result, the free-exciton-emission (FX) is obvious and the full-width at half maximum (FWHM) of donor-bound-exciton-emission (D0X) reduces from 8.63 meV (ZnO) to 6.05 meV. The ZnO E1 mode signal (433 cm-1) is enhanced in Raman spectrum. XRD patterns of Zn1-xCuxO (0 ≤ x < 0.66) epilayers were displayed the wurtzite and cubic structure co-exist when the Cu cell temperature (TCu)= 1100 oC. The ZnCuO epilayers of TCu from 700oC to 1200oC are all demonstrated n-type. The carrier concentration is reduced with increasing Cu flux from -5.0 × 1017 cm-3 to -4.3 × 1013 cm-3. However, the p-type ZnO epilayers are demonstrated by co-doped Ga into ZnCuO and the carrier concentration is around 5×1014 cm-3.
Furthermore, we report the characterization of nano-size ZnO powder synthesized via microwave assisted heating of Zn(CH3COO)2‧2H2O and NaHCO3 solution with deionized water as the solvent. The as-synthesized ZnO powder was calcined at temperatures from 400 to 800oC for 8 hr. The XRD and Fourier transform infrared spectroscopy (FTIR) spectra revealed pure wurtzite structure for the ZnO nanopowder (NP) calcined at 800oC. Scanning electron microscopy (SEM) images showed that the size and uniformity of ZnO NP increases with the calcination temperature raising. Significant UV emission at 373 nm has been observed in the PL spectra of the as-synthesized and calcined ZnO NP. Enhanced PL intensity and reduced FWHM for ZnO NP synthesized at higher calcination temperature are shown in our results. According to this base, we synthesize the MgZnO nanopowders with different Mg contents by the microwave heating technique. The difference between the designed, estimated Mg content, and different orders of adding in the synthesized samples are discussed.

並列關鍵字

p-type ZnO ； ZnCuO ； Cu-Ga codoped ； PA-MBE

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