高速850nm砷化鎵垂直共振腔面射型雷射設計與研究

Investigation of 850 nm GaAs Vertical Cavity Surface Emitting Lasers

梁尚封(Shan-Fong Leong)

指導教授 ： 吳肇欣

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201602985

摘要

本論文探討短波長850奈米紅外光高速垂直共振腔面射型雷射利用低電容厚鈍化層之光調變高頻頻域量測與高速眼圖頻域量測。針對鋅擴散與傳統垂直共振腔面射型雷射在小訊號模型之共振腔鏡面阻抗進行分析。論文內容包含磊晶結構設計、製程步驟與優化、光電直流特性分析、高頻頻域量測、小訊號模型分析和高速時域眼圖量測。
第一章，將介紹光通訊之優勢及垂直共振腔面射型雷射的發展背景和未來展望，探討850奈米短波長在通訊上之應用和高頻高速雷射的基本物理之限制。
第二章，利用軟體PICS3D模擬垂直共振腔面射型雷射主動區內不同銦比例觀察其高頻特性之表現。參雜高銦之主動區，對整體轉移函數是提升，原因為本質函數內的閾值電流降低和微分增益提高。藉由四乘四Luttinger-kohn的等效質量理論描述重價帶與輕價帶的價帶次能帶劈裂，探討高形變材料能帶電子電洞之分布，提高調變頻率之垂直共振腔面射型雷射之主動區設計。
第三章，介紹垂直共振腔面射型雷射之研製。探討傳統氧化式和鋅擴散氧化式垂直共振腔面射型雷射在相同孔徑、控溫25℃下的直流特性之分析，包含光電曲線、光頻譜分析、微分電阻、最大量子效率和光電轉換效率之量測。
第四章，探討傳統氧化式和鋅擴散氧化式垂直共振腔面射型雷射的調變速度和能源效率做分析，眼圖和誤碼率之量測。最後，利用小訊號等校電路模型萃取元件內部之電阻、電容和電感進行分析。探討雷射本質轉移函數和電路轉移函數之高頻限制，由熱效應、阻尼效應和電路寄生效應的三個面向進行討論。最後進行結構及製程的優化達到更高更快的資料傳輸與調變速度。

關鍵字

垂直共振腔面射型雷射 ； 共振腔 ； 調變 ； 光學元件 ； 小訊號等校電路模型 ； 轉移函數 ； 鋅擴散

並列摘要

In the thesis, the optical modulation and on-off keying (OOK) open eye diagram of infrared 850 nm Vertical Cavity Surface Emitting Lasers (VCSELs) with low capacitance and thick benzocyclobutene (BCB) passivation layer are measured. We compare zinc-diffusion oxide-confined VCSEL with conventional oxide-confined VCSEL of the influence of mirror resistance within distributed Bragg reflector (DBR) by utilizing small-signal equivalent circuit model.
The advantages of the optical communication and the background of VCSELs will be introduced. Then, we discuss the application of the 850 nm VCSEL and the research motivation. After understanding the fundamental physics of the diode laser, we propose different structures and process designs to improve optical modulation bandwidths.
Moreover, we obtain the optimal structure that has low threshold current, high differential gain and high modulation bandwidths by simulating the active region structures. The analysis of the optical and electrical characteristics for the VCSELs is demonstrated by PICS3D from Crosslight Software, Inc., i.e. reflectivity of DBRs, electric fields, refractive index, gain spectrum and RF modulation. Based on 4×4 Luttinger-kohn Hamiltonian, we describe the valence-subband structure in barrier quantum well model.
We optimize the process flow of VCSEL by using the concept of electrical transfer function from small-signal equivalent circuit model. We measure the optical and electrical dc characteristic of zinc-diffusion oxide-confined and conventional oxide-confined VCSEL with aperture diameter of 5 µm. Zinc-diffusion VCSELs have lower threshold current, lower differential resistance, higher slope efficiency and higher wall-plug efficiency due to impurity-induced disordering for the tailoring of bandgap and refraction by intermixing the layers of semiconductor heterostructures, creating undamaged homogeneous alloys of average composition.
We analyze and measure the modulation ability of the zinc-diffusion and conventional VCSELs with same aperture diameter of 5 μm at 25℃. Then, we measure the eye diagram and bit error rate. At last, the small-signal equivalent circuit parameters of the devices with aperture diameter of 5 μm at bias 5×, 10× and 15×Ith mA are extracted. We analyze the modulation speed limitation by three aspects including thermal effect, damping effect and parasitic effect. Finally, we discuss how to improve the modulation speed by optimization of the layer structures and process flows.

並列關鍵字

VCSEL ； Cavity ； Modulation ； Optical Device ； Small-signal Model ； Transfer Function ； Zinc-diffusion

參考文獻

[1] The growth of the internet of things by 2014.

[3] The 2016 Ethernet Roadmap.

[5] IEEE 802.3. Ethernet.

[6] Koomey, J., “Worldwide electricity used in data centers,” Environ. Res. Lett., vol. 3, no. 3, p. 1–8, 2008.

[7] Soda, Iga, Kitahara and Yasuharu Suematsu, “GaInAsP/InP Surface Emitting Injection Lasers,” JPN. J. APPL. PHYS. vol. 18, no. 12, 1979.