臺灣博碩士論文加值系統

本論文係利用化學氣相沉積爐的方式將硒化鋅異質磊晶於砷化鎵基板上,磊晶成長完成之硒化鋅薄膜分別藉由SEM, SIMS, XRD 和PL 加以探討薄膜特性,因砷化鎵和硒化鋅晶格只有0.27%不匹配,吾人觀察得知硒化鋅磊晶層之表面平滑,硒和鋅成份分佈均勻而且薄膜結構為單晶。
由PL光譜在13K時測得硒化鋅薄膜在446nm(2.78eV)有一能隙光造成的NBE peak。隨著溫度的升高NBE peak強度減小,線寬變寬並且波峰往長波長偏移。而經銦摻雜的硒化鋅薄膜在454nm(2.73eV)有一施體階造成的peak。
在元件的製作方面,利用此硒化鋅異質磊晶層製作平面型MSM光檢測器，測得最佳短波長光電元件。由實驗得知在無抗反射層的情況下,Au-ZnSe/GaAs MSM-PD and ITO-ZnSe/GaAs MAM-PD光檢測器在固定偏壓10V、470nm的照光情況下，其光電流響應度為4.89A/W and 5.75 A/W。
另外在400nm至700nm光波長範圍內，元件於470nm照光時有最強的光電流響應度，這個結果證實了 ZnSe/GaAs MSM光檢測器將適合的應用於短波長之光檢測。當偏壓於10V時，我們可以測量得其光響應時間半高寬為16ns and 15ns。
在 self-aligned ZnSe/GaAs 異質光電晶體之製作方面,測得元件在短波長470nm藍光波段時亦具有最大光電流響應。由結果得知將硒化鋅成長於砷化鎵基板所製作之光電元件極適合來製作短波長藍光偵測器,在未來短波長元件的OEIC應用上極具潛力。

In this thesis, the ZnSe epilayers were grown on an oriented-(100) GaAs substrate using low cost furnace CVD system. The ZnSe epilayer were analyzed by using SEM, SIMS, XRD, and PL measurements. Because there is approximately 0.27% lattice mismatch only between ZnSe and GaAs substrate, the surface morphology of the ZnSe epilayer is smooth, the distribution of the main elements is uniformity and the ZnSe epilayer is to a single crystal.
From the PL measurement at 13K for the ZnSe epilayer, it indicates the NBE excitation emission is at 446nm(2.78eV). With the increasing of the temperature, the intensities of the NBE peak decrease and the FWHM becomes broader. Then it shifts toward longer wavelengths region. For the In-doped ZnSe epilayer, the D1 peak at 454nm(2.73Ev) can be observed due to the In atoms replace the Zn sites that induce the transition between a shallow donor and the valence band level.
ZnSe/GaAs planar metal-semiconductor-metal photodetectors are promising candidates for optoelectronic integration of short-wavelength components. The Au-ZnSe/GaAs MSM-PD and ITO-ZnSe/GaAs MSM-PD photodetector without any passivation and antireflection coating exhibits the photo-responsivity are 4.89A/W and 5.75A/W respectively at 470nm light wavelength , 10V bias. The fabricated photodetector has the strongest photo-responsivity in the wavelength of 470nm. The results demonstrate the studying ZnSe/GaAs MSM photodetector will be suitable for the applications of the short wavelength photo-detectors. We can measurement yielded an FWHM of 16ns and 15ns for a bias voltage of 10V.
In addition, the novel structure of self-aligned ZnSe/GaAs heterojunction photo-transistor also reveals the strong photo-responsivity in 470nm. It demonstrated the studying of photodetectors based on ZnSe grown on GaAs substrate are useful to develop low cost short wavelength blue light opto-electronic devices and have a great potential for the applications of the short wavelength OEIC.

CHAPTER 1. Introduction …..………………………..……….…1
1-1. Overview …………….....……….……..….......……...…….1
1-2. Thesis Outline ……….…..………........…....…….…….….3
CHAPTER 2. Theoretical Analysis of ZnSe/GaAs
Heteroepitaxy ………………………………..……5
2-1. Introduction ………………………………………………..5
2-2. Growth Process ……………………..…….….…...……....5
2-2-1. Kinetics of Epitaxial Growth………………………...6
2-2-2. Gas-Phase Mass Transfer………………………….…8
2-2-3. Boundary Layer Theory………………………..……..9
2-3. ZnSe/GaAs Heteroepitaxy …………….......…..….…....10
2-4. ZnSe/GaAs Heterojunction ……………..……….….…11
2-5. In-Doped ZnSe ….…......…………………….…………..14
2-6. Wet Etching …….………......………......…….….………15
2-7. Diffusion …………………......…………....….…..……...16
CHAPTER 3. Quality Analyses of ZnSe/GaAs Heterojunction
Epilayer and Optical Properities .……………….18
3-1. Introduction ………………………………………….…18
3-2. Surface Morphologies …………………..............…….18
3-3. Uniformity …………….......…………..….................…..20
3-4. Crystallographic Properties ……………................….21
3-5. Photo-Luminescence Properties ………………...…23
3-6. Conclusions ……..…….......…………......…...........…....25
CHAPTER 4. Theory and Fabrication of ZnSe/GaAs Metal-
Semiconductor-Metal Photodetector………..….27
4-1. Introduction …………….......……………..................….27
4-2. Theoretical Analysis ……………...…..................…..29
4-2-1. Metal-Semiconductor-Metal junction …...…..…29
4-2-2. Photo-Current Mechanisms ……...…….......….30
4-2-3. Photo-Current Responsivity………....…….......31
4-2-4. Quantum Efficienc ………………………..……....32
4-2-5. Speed Response …………….……………........….32
4-2-6. Dark Current ………………....………………......….34
4-3. Device Structure and Fabrication ….……...….…..35
4-3-1. Device Structure ………...…………………..........….35
4-3-2. ZnSe Epilayer Prepared …….………….….....….36
4-3-3. Device Isolation ……..……....….………..….............36
4-3-4. Schottky Contact Metallization ……..………….....37
4-3-5. Recessed-Cathode………………………..………...37
4-3-6. Absorption Profile …………………….….………...38
CHAPTER 5. Results and Discussions of ZnSe/GaAs Metal-
Semiconductor-Metal Photodetector ….………..39
5-1. Introduction……………………………………………… 39
5-2. Schottky Barrier Height……………………….………..40
5-2-1. Capacitance-Voltage Measurement ……….….…40
5-2-2. Measurement of Barrier Height ……………….…41
5-3. Transmittance ….…………………………….……42
5-4. Photo-Current Responsivity ……………..…………..42
5-4-1. Conventional MSM-PD ….………………..………..43
5-4-2. Recessed-electrode MSM-PD ………………..……45
5-5. Impulse Response Time ……………..…...............…….46
5-5-1. Conventional MSM-PD ….……………………..…..46
5-5-2. Recessed-electrode MSM-PD ……………………..47
5-6. Conclusions …………..…….....…..………..….................47
CHAPTER 6. Theory and Fabrication of ZnSe/GaAs
Heterojunction Photo-Transistor………….…..49
6-1. Introduction …………….....…..…………....................49
6-2. Theoretical Analysis …………….......………….……50
6-2-1. Emitter Injection Efficiency …………..…….50
6-2-2. ZnSe/GaAs Heterojunction photo-Transistor..50
6-2-3. High-Frequency Characteristics ……..………..51
6-3. Devices Structure and Fabrication ………………..52
6-3-1. Device Structure ………….….………..……....….52
6-3-2. Emitter Metallization ……………....……..….....….53
6-3-3. Base Metallization …………………………........….53
6-3-4. Device Isolation…………………………………….54
6-3-5. Collector Metallization…………………………….54
6-4. Results and Optical Propertis……………...…………..54
6-4-1. B-E and B-C Junction Diodes…………………….55
6-4-2. ZnSe/GaAs Heterojunction Photo-Transistor….55
6-5. Conclusions……………..………………………..……..57
CHAPTER 7. Conclusions ……..…………….....……..................….58
7-1. Summary …………….………….....………................….58
7-2. Further Expectation ….………………….…..........…....60
References ………………..………………………....….………..................…....61
Figures ………..………....……………………………...…………...............…....78

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