臺灣博碩士論文加值系統

本論文主要以具有較低成本且同時擁有低電阻率和高光穿透率的透明導電氧化物薄膜做為研究目標。
首先我們利用技術已成熟且製程相對穩定、再現性高的共濺鍍系統來成長三元化合物氧化錫銦鋅透明導電薄膜。元素來源部份我們選擇已商業化、可順利取得之氧化錫銦(ITO, 10wt% Sn)及氧化鋅(ZnO)做為靶材，經由調整不同靶材之濺鍍功率及相關參數，以取得初步樣品。這些樣品經過元素比、結晶性、導電性及光穿透度等分析，決定出最佳製程參數。該製程參數樣品在光電特性和材料成本上，亦取得最佳平衡。
為進一步提升薄膜的導電性，以應用於較大面積元件市場(例如：太陽能元件、觸控玻璃等)，以及後續實驗目標，所以我們透過電子束蒸鍍系統，沉積一層非常薄的銦金屬層於氧化錫銦鋅與玻璃基板之間，期許此架構能兼俱超薄金屬薄膜之導電性與透明導電薄膜之光穿透性。經由研究結果顯示，光電特性在未熱處理前，嚴重惡化。其主因乃後製程之氧化錫銦鋅薄膜於不同濺鍍基材表面(石英玻璃與銦金屬)，所成長之結構和元素比亦不同，但該實驗組經由適當熱處理後，將使電阻率大幅改善(~10-4 Ω-cm)，同時俱有優異的光穿透率(~93% @ 可見光譜範圍內)。Burstein-Moss effect 可說明此現象，主要是熱處理後的樣品，載子濃度提高了一個次方(~1021/cm3)，過高的載子濃度會使電子佔據傳導帶最低能帶(階)，進而影響光能隙或是光子的吸收。
最後，我們將此複層透明導電薄膜直接沉積於P型氮化鎵基材上。實驗結果顯示，有插入一層超薄銦金屬，在經過適當熱處理後的實驗組，和P型氮化鎵具有良好的歐姆接觸特性。其原因機制，應該是在後製程及熱處理過程中，氮化鎵表面少量的鎵向上擴散形成一極窄的高載子濃度電洞層，同時小量的鋅2+及銦3+原子佔據鎵空缺，使蕭特基能障降低，再配合大部份的銦原子擴散到上層氧化錫銦鋅層，使其形成退化性半導體，因此載子透過穿隧機制形成歐姆接觸。
後續將繼續將薄膜實作於完整LED結構上，以量測更多相關數據，以驗証其實務性及穩定性，及比較出光效率的優異性。

This thesis is mainly to lower cost with low resistivity and high optical transmittance of the transparent conductive oxide film as a research target.
The ternary compound zinc-indium-tin-oxide transparent conductive film were deposited using the co-sputtering system which the technology had matured and the process is relatively stable、high reproducibility. The source of targets, we selected already commercial and convenient obtained, were the indium tin oxide (ITO, 10wt% Sn) with the zinc oxide (ZnO) and through the adjustment of different target of power and related parameters to obtain preliminary samples. We determine the optimal process parameters by these samples through the elemental analysis of crystalline, electrical conductivity and optical transmittance. This process sample could achieve the best balance of the optical, electrical properties and materials costs.
To further enhance the conductivity of the films used in large-area components market (for example: solar cell modules, touch panel, etc.), and follow-up experiments so that we deposition a very thin indium metal layer between the zinc indium tin oxide with glass substrate by electron beam evaporation system. We hope that this architecture could concurrently good conductivity by thin metal films with good transmittance by transparent conductive oxide thin film. The results show that the optical and electrical properties were deterioration before the heat treatment. The main reason is the growth structure and elements of zinc-indium-tin-oxide thin films deposited at different material of substrate (quartz glass and indium metal) were different. Nevertheless, the resistivity and transmittance have significantly improved after heat treatment. Burstein,-Moss effect can explain this phenomenon, the carrier concentration of the heat-treated samples have increased an order of carrier concentration (~1021/cm3) which blocking the lowest states (filled states) in the conduction band from absorbing the photons.
Finally, we directly deposited this transparent conductive film on the p-GaN substrate. The experimental results show that the sample, insert a thin metal of indium, has a good Ohmic contact with P-type GaN after appropriate heat treatment. The mechanism of the result maybe is through a tunneling to form Ohmic contact due to a small amount of the gallium out-diffusion from p-GaN surface could create a narrowness deep acceptor-like (increases in hole concentration) region during post-annealing treatment while the In3+ or Zn2+ atoms diffused into gallium vacancies sites reduction in the Schottky barrier height and most of indium metal atoms spread to the upper ZITO layer to form the degenerative semiconductor.
Follow-up will continue to implement the films at LED and measure more data to verify its stability and relatively light efficiency.

摘要 ........................................................I
Abstract ...................................................III
誌謝 .......................................................V
Contents ...................................................VI
Table Captions ..............................................IX
Figure Captions .............................................XI
Chapter 1 Introduction ...................................1
1.1 Background ........................................1
1.2 History of TCO .....................................3
1.3 Motivation .........................................5
1.4 Overview of this thesis ...............................7
Chapter 2 Basic theory .................................11
2.1 Theory of co-sputter system ..........................11
2.2 Hall effect .........................................13
2.3 X-ray diffraction (XRD) .............................14
2.4 Transmission line model (TLM) .......................16
Chapter 3 Experiment result of Zn-In-Sn-O (ZITO) and ZITO/In thin films ..............................21
3.1 The procedures of ZITO thin films .....................23
3.1-1 Clean samples ...................................23
3.1-2 Co-Sputtering procedures .........................23
3.1-3 The influence and result of the sputter power .........24
3.1-4 The influence and result of the substrate temperature .28
3.1-5 The influence and result of the oxygen partial pressure .29
3.1-6 The influence and result of post annealing treatment ...30
3.2 The procedures of ZITO/In thin films ...................32
3.2-1 E-beam evaporation procedures ....................32
3.2-2 The influence and result of the In metal layer .........33
3.2-3 The influence and result of the In metal layer after post annealing treatment ...............................39
3.3 Summary ..........................................44
Chapter 4 Investigation of p type GaN contact with ZITO/In thin film ........................................79
4.1 The history and properties of GaN-base material ..........79
4.2 Procedure of P type GaN ..............................82
4.3 Procedure of TLM ...................................82
4.4 Experiment results and discussion ......................84
Chapter 5 Conclusion and Future work ................... 94
5.1 Conclusion ..........................................94
5.2 Future work ........................................95
Reference ..................................................96

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