利用 Si-δ-摻雜之 AlGaAs/InGaAs 異質結構中的二維電子氣開發之超高靈敏霍爾磁性感測器暨元件特性分析

本論文的研究主題包括四大部分，分別細述如下: (一): 樣品的製作與元件特性分析。量測系統設立及量測條件介紹。(二): 溫度相依的載子移動在矽 -摻雜AlGaAs/InGaAs/AlGaAs 量子井與不同間隔層厚度變化下的霍爾效應量測。(三): 時間相依下的負及正光電導變化分別在不同溫度, 不同入射光能量及強度下的時間變化現象。(四): 磁感測器應用市場及元件特性的標竿比較。其中核心的學術研究討論分述在在本文章節 (3) (4)。章節(3): 討論分析霍爾效應特性變化，針對具不同間隔層 (Space layer) 厚度（tS = 5、10和15 nm）的雙Si δ摻雜的AlGaAs / InGaAs / AlGaAs量子井（QW）結構的霍爾效應現象，分析溫度範圍為（T = 40〜300 K）。對於tS = 10和15 nm，觀察到了有趣的片電子濃度（Sheet carrier concentration, n2D（T））磁滯曲線，而對於tS = 5 nm，則沒有觀察到。提出了一個模型，該模型分別涉及兩個不同的活化位能障 (Activation barrier)，分別由主動層量子井中的電子和δ摻雜層中的離子化 (Ionized) 電子所貢獻，這就是所謂的磁滯曲線的來源所在。但是，對於足夠小的tS（= 5 nm ≦ 2.5s，其中s = 2.0 nm是高斯擬合 (Gaussian Fit) 得出Si-δ摻雜輪廓的標準差），靠近QW附近的Si摻雜分佈，扮演起類似特殊形式的 “Modulation doping" 作用，而不可被視為是理想的δ摻雜。 QW附近的Si原子數量有效地增加了n2D的水平，因此沒有觀察到磁滯曲線。最後，也討論了tS 對主動層QW通道中電子遷移率與溫度依賴性的影響。在章節(4): 過去Si摻雜的AlGaAs / InGaAs / AlGaAs量子阱（QW）結構是廣泛被接受作為現代電子和光電元件的核心元素之一。於此，系統地研究了在各種溫度（T = 80〜300 K）和各種入射光子能量（Ein = 1.10〜1.88 eV）和強度下，在對稱的Si δ雙摻雜AlGaAs / InGaAs / AlGaAs QW結構中，沿主動層InGaAs QW通道的光電導譜 (Photoconductivity) 隨時間變化。除了正光電導性 (PPC, Positive photoconductivity) 外，同時還觀察到負光電導（NPC, Negative photoconductivity），此歸因於兩個不同的起因。對於Ein = 1.51〜1.61 eV 在T = 180和240 K溫度條件下，光激發的電子被座落在InGaAs QW層導帶上方的界面態 (Interface state) 所捕獲是NPC曲線的起源之一。對於Ein = 1.10〜1.63 eV的T = 80 ~ 120 K，由於冷卻過程不足夠長的原因，引起主動層InGaAs QW中電子的未能有充分時間回到穩態狀態，進而呈現 ”過飽和”的不穩定暫態，當被光激發後，電子快速被捕捉是另一個原因。在章節(5): 主要討論商業化應用目前的三大應用，電流傳感器 (C.T., Current Transducer)、編碼器 (Encoder) 及光學防手震 (O.I.S., Optical Image Stabilizer)。共同要求的特性有靈敏度(Sensitivity)、溫度係數，響應速度和雜訊。而靈敏度和霍爾電壓有關，溫度係數和載子濃度隨溫度的變化有關，響應速度與載子遷移率(Mobility) 有關，雜訊與通道品質與矽摻雜因為離子化形成 Si+ 正離子與電子，其間的庫倫力干擾有關。

關鍵字

III-V 霍爾磁性感測元件；矽 δ-摻雜； AlGaAs/InGaAs/AlGaAs 量子井；二維電子氣；霍爾效應分析；電荷載子傳輸；溫度相依之遲滯效應； InGaAs 主動層通道； InGaAs 介面狀態；光激發負光導；光激發光導

並列摘要

This thesis include four major parts : Part I: Samples fabrication and characterization of Si-δ-doped AlGaAs/InGaAs/AlGaAs quantum well structures. Part II: Temperature-dependent charge-carrier transport between Si δ-doped layer and AlGaAs/InGaAs/AlGaAs quantum well with various space layer thicknesses measured by Hall-effect analysis Part III: Time dependence of negative and positive photoconductivity for Si δ-doped AlGaAs/InGaAs/AlGaAs quantum well under various temperatures and various incident photon energies and intensities Part IV: Applications market and device characterization and performance benchmarks. The major researchs and discussions were addressed in Chapter 3 and Chapter 4. In Chapter 3, discuss about: Temperature (T = 40 ~ 300 K) dependence of Hall-effect analysis on the dual Si δ-doped AlGaAs/InGaAs/AlGaAs quantum-well (QW) structures with various space layer thicknesses (tS = 5, 10 and 15 nm) was performed. An interesting hysteresis curve of electron sheet concentration (n2D(T)) was observed for tS = 10 and 15 nm but not for tS = 5 nm. A model involving two different activation barriers encountered respectively by electrons in the active QW and by electrons in the δ-doped layers is proposed to account for the hysteresis curve. However, for small enough tS (= 5 nm  2.5s, where s = 2.0 nm is the standard deviation of the Gaussian fit to the Si-δ-doped profile), the distribution of Si dopants near active QW acted as a specific form of “modulation doping” and can not be regarded as an ideal δ-doping. The amount of Si atoms near QW effectively increase the level of n2D, and hence no hysteresis curve was observed. Finally, effects from tS on the T-dependence of electron mobility in active QW channel are also discussed. In Chapter 4, discuss about : Si δ-doped AlGaAs/InGaAs/AlGaAs quantum well (QW) structure is commonly adopted as one of the core elements in modern electric and optoelectronic devices. Here, the time dependent photoconductivity spectra along the active InGaAs QW channel in a dual and symmetric Si δ-doped AlGaAs/InGaAs/AlGaAs QW structure are systematically studied under various temperatures (T = 80 ~ 300 K) and various incident photon energies (Ein = 1.10 ~ 1.88 eV) and intensities. In addition to positive photoconductivity, negative photoconductivity (NPC) was observed and attributed to two origins. For T = 180 ~ 240 K with Ein = 1.51 ~ 1.61 eV, the trapping of the photo-excited electrons by the interface states located inside the conduction band of InGaAs QW layer is one of the origins for NPC curves. For T = 80 ~ 120 K with Ein = 1.10 ~ 1.63 eV, the photoexcitation of the excess “supersaturated” electrons within the active InGaAs QW caused by the short cooling process is another origin. In Chapter 5, Mainly mentioned about the three major commercial applications, Current Transducer (C.T.), encoders and Optical Image Stabilizer (O.I.S.). Commonly required characteristics are sensitivity, temperature coefficient, response speed and noise. Sensitivity is related to Hall voltage. Temperature coefficients correspond to carrier concentration varied with temperature. Response speed is related to carrier mobility. Noise was directly relative to channel quality and Coulombic scattering of impurities It is due to the silicon doping and after free ionization to form Si+ positive ions and electron. Then the interference of the Coulomb force is related.

並列關鍵字

III-V Hall effect magnetic sensor ； Si-δ-doping ； AlGaAs/InGaAs/AlGaAs quantum well ； 2DEG ； Hall-effect analysis ； Charge-carrier transport ； T-dependent hysteresis effect ； InGaAs active channel ； Interface states of InGaAs ； Negative photoconductivity ； Photoconductivity