面射型雷射主要作為光纖通訊中的發射光源。由於面射型雷射發光具有圓形光束，不需要切割即可直接在晶圓上做量測，低操作電流與高調變能力，因此相對於側射型雷射有更好的吸引力。
在論文中將展示面射型雷射的製作。首先利用PECVD鍍SiO2於磊晶片上，透過黃光與蝕刻定義所需要區域。SiO2主要作為阻擋ICP蝕刻用，目的在於蝕刻出AlAs層，接著試片進行濕氧化的製程。
影響蝕刻的條件包括ICP功率、RIE功率、壓力與蝕刻氣體。一開始是以Ar與BCl3作為蝕刻氣體，但蝕刻速率仍不足。當加入N2後，蝕刻速率明顯地由1.8μm/min提昇至3.6μm/min。蝕刻後的情形與以原子力顯微鏡與掃描式電子顯微鏡做量測。
濕氧化製程的面射型雷射能夠侷限側向的電流減少損失，另一方面
能增加光的侷限。鋁在潮濕的環境下會產生氧化物。將氮氣通入水瓶以氣泡的方式產生水氣，再通入高溫爐管中進行濕氧化製程。透過條件的改變，控制濕氧的情形。氧化的結果由顯微鏡與CCD做觀察。
P型與N型電極最後以熱蒸鍍的方式完成，並在爐管中進行回火。元件特性透過輸入電流與輸出功率關係圖和頻譜圖的量測獲得。證明面射型雷射能夠成功的實現。
在最後一部分則是元件的量測與探討。藉由SiO2阻擋漏電路徑，使得特性有效提升。在變溫的L-I量測中，臨限電流會隨著溫度改變，並且在特定溫度時有最小值。為了探討熱對於元件的影響，改變氧化孔徑，並量測熱阻，然而，熱阻不僅受到氧化孔徑的影響，受到磊晶片均勻性的影響也是很大。最後進行InGaAs/GaAs微共振腔體的光學量測，有機會藉著熱位移到高反射率區，具有實現長波長面射型雷射於砷化鎵基板的可能性。

The VCSELs are mainly used as light source for optical communication. The VCSELs are more attractive than edge-emitting lasers due to a circular output beam generated, suitable for on-wafer testing, low current consumption, and high frequency modulation capability.
In the thesis, the fabrication of VCSELs is demonstrated. First, SiO2 is deposited by PECVD on the surface of epitaxial wafer. The SiO2 layer is defined by lithography technology and etched. The SiO2 is then taken as hard mask for ICP (inductively coupled plasma) etch. The ICP is used to etch DBRs in order to expose Al0.98Ga0.02As layer, before transferring the sample for oxidation process.
The parameters relevant to ICP etching include ICP power, RIE power, pressure and species of gas. Initially, argon and boron trichloride are used but the resultant etching rate is slow. The etching rate increases from ~1.8μm/min to ~3.6μm/min with and without N2 incorporation, respectively. Surface roughness and etching profile are characterized by AFM and SEM.
Oxide-confined VCSELs are designed to confine the lateral electrical loss and increase the optical confinement. The aluminum has a tendency to become oxidized in wet environment. Water vapor is blow by nitrogen through bubble system and is then transferred to high temperature furnace. By modulating these parameters, a large portion of an aluminum layer is expected to oxidize under control. The oxidation rate is assessed by CCD image.
Finally, p and n contacts are deposited by thermal evaporator and then annealed in furnace. The L-I curve and lasing spectrum are two of most important figures of merit for lasers. In result, the VCSELs are successfully fabricated and measured.
The characteristics and measurement of VCSELs are analyzed in the last chapter. SiO2 layer is taken as the isolation to block the leakage path in order to improve the efficiency. Minimum threshold currents can be determined from L-I curves obtained with various temperatures. Different thermal resistances are measured with various diameters of oxide aperture in order to recognize the thermal effect. The thermal resistance is not only dependent on the oxide aperture but also on the film uniformity of wafer. Characterization of InGaAs/GaAs microcavity is measured in last section. The wavelength could be extended to longer wavelength by heating. It has a potential to realize GaAs-based VCSELs emitting at long wavelength.

Chapter 1
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Chapter 2
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Chapter 3
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Chapter 4
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Chapter 5
[1] E. Pougeoise, P. Gilet, P. Grosse, S. Poncet, A. Chelnokov, J. M. Gerard, G. Bourgeoise, R. Stevens, R. Hamelin, M. Hammar, J. Berggren and P. Sundgren, “Strained InGaAs quantum well vertical cavity surface emitting lasers emitting at 1.3μm,” Electron. Lett., Vol, 42, No. 10, pp. 584-586, 2006.
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