本論文利用光調制光譜(Photoreflectance, PR)、光激發螢光光譜(Photolumenience, PL)、拉曼光譜(Raman Spectroscopy)及高解析X光擺動曲線量測研究一系列由氣態源分子束磊晶系統成長於(100)半絕緣砷化鎵基板上的氮磷化銦鎵/砷化鎵(InGaPN/GaAs)異質結構之光電特性，如能隙值、能帶排列、二維電子氣、內建電場、載子侷域化、有序效應、應變、價帶分裂值…等。首先，在室溫下量測In0.54Ga0.46P1-yNy/GaAs (y = 0 – 2%)樣品的PR及PL光譜，隨著其含氮的增加，其能量峰值產生紅位移的現象且PR光譜中出現了額外的訊號。顯示當氮加入時，InGaPN的能隙值隨著含氮量的增加而快速減小，其額外的訊號則代表InGaPN和GaAs的能帶排列狀態由型式I逐漸轉變為型式II，因而在界面間形成了二維電子氣(Two-Dimensional Electron Gas, 2DEG)，且2DEG的能階數目隨著氮濃度而增加。其能帶排列狀態的轉變則是由於導電帶的下降所致，不同氮濃度的樣品的能隙值及其2DEG能階間的躍遷能量均可由譜線的位置決定。另外，與氮含量相關的拋物參數(Bowing Parameter)也由實驗結果求得。
其次，我們量測溫度從25到300 K的InGaPN/GaAs異質結構的PR及PL光譜，獲得能隙值隨溫度的變化曲線，並與Varshni方程式做最小平方擬合求得InGaPN的Varshni係數α及β值。在含氮的樣品中，其低溫的PL光譜同時出現分別來自自由激子及侷域激子復合的兩個峰值；然而磷化銦鎵(InGaP)的PL光譜則只觀察到自由激子復合的訊號，這可歸因於InGaPN樣品在低溫時形成氮團簇(clusters)所導致的載子侷域化。此侷域激子復合的訊號，在PR光譜中並未出現。
本論文同時利用室溫下的拉曼光譜及PL光譜對InGaPN的弱有序效應進行定量的研究。InGaPN磊晶層裡的有序效應是由於晶體從閃鋅結構過渡到CuPt結構以及形成了氮化鎵(GaN)團簇的影響。在PL光譜方面，隨著氮濃度的增加，樣品的有序效應隨著增加、品質下降，產生了更多的非輻射中心，造成PL強度迅速減小。在拉曼光譜方面，我們分析了InGaPN在130和1000 cm-1之間的拉曼模，並使用極化的拉曼光譜證明更多氮的摻雜會使InGaPN變得更有序。在730 cm-1左右出現的寬廣的拉曼訊號，則歸因於類似氮化銦鎵(InGaN)的縱向光性聲子所造成。
最後，我們並使用高解析X光擺動曲線與不同溫度下的PR光譜研究InGaPN/GaAs異質結構的磊晶應變和原子有序效應。所有在GaAs緩衝層上的磊晶層皆具有同調的壓縮應變，InGaPN的晶格常數則遵守bowing效應，不再追隨Vegard’s定律。InGaPN的價帶分裂值和自旋軌道分裂值均由PR光譜獲得。當氮濃度增加時，磊晶層和GaAs之間的晶格不匹配(壓縮應變)降低，然而價帶分裂值卻增加，代表InGaPN的有序程度上升。除此之外，InGaPN的有序參數η亦可由PR獲得之價帶分裂值推得。
根據上述的結果，可確知利用螢光光譜、拉曼光譜、光調制光譜及高解析X光擺動曲線可有效的研究InGaPN/GaAs異質結構的許多基礎光學及結構上的特性，對於闡明微量的氮在III-N-V半導體中的影響非常有幫助，並能改進由InGaP/GaAs材料所建構的電子元件之性能，例如：電洞阻擋異質接面雙極性電晶體等等，促進光電及電子產業水準的提升。

This dissertation studies the electro-optical properties of a series of In0.54Ga0.46P1-yNy/GaAs heterostructures grown on (100) GaAs semi-insulating substrate by gas source molecular beam epitaxy (GSMBE). Various characterization techniques, such as photoreflectance (PR), photoluminescence (PL), Raman spectroscopy, and high-resolution x-ray rocking curve (XRC) measurements are employed in this work.
Room-temperature PR and PL spectra are measured for a series of In0.54Ga0.46P1-yNy/GaAs (y = 0 – 2%) samples grown by GSMBE. The redshifts of the PR and PL peaks indicate that the bandgap of InGaPN is dramatically reduced as nitrogen is incorporated. The emergence of additional peaks in PR spectra as nitrogen is incorporated indicates that the band alignment switches from type I to type II, due to the lowering of the conduction band, thus forming a two-dimensional electron gas (2DEG) in the interface region between InGaPN and GaAs. The bandgap energy and transition energies between the confined levels in the 2DEG are determined for samples with various nitrogen concentrations y. The number of confined levels in the 2DEG is found to increase with y; the composition-dependent bowing parameter is determined.
Next, PR and PL spectra are measured for the InGaPN/GaAs heterostructures at temperatures ranging from 25 to 300 K. The transition energies of the band edge at various temperatures are measured and least-squares fitted to the Varshni equation. With N incorporated, the PL peak energy exhibits a particular behaviour with temperature, which isn’t observed in the PR spectra. At low temperatures, two peaks from the recombination of free and localized excitons, respectively, are observed simultaneously in the PL spectra of InGaPN while only one peak corresponding to the recombination of free excitons appears in that of InGaP. This is attributed to carrier localization resulting from N clusters in the samples.
The effect of weak ordering on InGaPN is also quantitatively studied by room-temperature Raman and PL spectroscopy in this work. The PL intensity rapidly decreases as the nitrogen concentration increases, implying that more nonradiative centers are generated by the ordering effect and the degradation of the samples. The Raman modes of InGaPN between 130 and 1000 cm-1 are analyzed. Polarized Raman spectra reveal that the InGaPN layers become more ordered as more nitrogen is incorporated. A broad Raman structure that appeared around 730 cm-1 is attributed to an InGaN-like LO-phonon mode. The transition of the crystal structure from the zinc blende to CuPt structure and the formation of GaN clusters are responsible for the ordering effect in the InGaPN layer.
Finally, both the epitaxial-strain and atomic-ordering effects in the InGaPN/GaAs heterostructures are characterized by high-resolution XRC measurements and PR spectra at various temperatures. All epilayers on the GaAs buffer layer exhibit coherent compressive strain. The lattice constant of InGaPN follows a bowing effect instead of Vegard’s law. The valence-band splitting (VBS) and spin-orbit splitting of InGaPN are obtained from PR spectra. As nitrogen concentration increases, the lattice mismatch (the compressive strain) between the epilayer and GaAs substrate decreases while the VBS increases, which implies an increase in the degree of ordering of InGaPN. In addition, the order parameter η of InGaPN is deduced from the VBS obtained from PR spectra.
According to the above researches, many fundamental optical and structural properties of the InGaPN/GaAs heterostructures are determined. These are very helpful to clarify the effect of the small amount of nitrogen on III-N-V semiconductors and improve the performance of InGaP/GaAs-based electronic devices, such as blocked-hole heterojunction bipolar transistors.

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