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研究生： Nguyen Thi Anh Nguyet
Nguyen Thi Anh Nguyet
論文名稱： P型氮化硼的導電性
Electrical conductance of P-type Boron Nitride
指導教授： 賴昆佑
Kun-Yu Lai
Le Vu Tuan Hung
Le Vu Tuan Hung
口試委員:
學位類別： 碩士
Master
系所名稱： 理學院 - 光電科學與工程學系
Department of Optics and Photonics
論文出版年： 2019
畢業學年度： 107
語文別： 英文
論文頁數： 62
中文關鍵詞： P型氮化硼
外文關鍵詞： Electrical conductance of P-type Boron Nitride
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    • CHINESE ABSTRACT
    深紫外線 [Deep Ultraviolet (DUV), λ ≤ 290nm] 發光二極體 (light-emitting diode, LED) 已經在各種應用中逐漸取代傳統的紫外線光源。然而，DUV LED的外部量子效率 (external quantum efficiency, EQE) 依然難以超過10%，這主要是因為DUV LED的p型導電層為摻雜鎂 (Mg-doped) 的AlxGa1-xN，而p型AlxGa1-xN受體的活化能很高（170 mev ~ 510 meV)，難以產生足夠的電洞p型氮化硼（BN高能隙（~ 6 eV)，也有很低的受體活化能 (~ 31 meV)，可以同時展現高穿透、高導電的特性，很適合用在DUV LED。為了研究p-BN的導電性，我們嘗試不同的金屬材料與退火條件也調整了p-BN的磊晶結構，並利用利用霍爾效應比較p-BN與p-GaN的導電性。我們發現，以低壓成長的3-nm InGaN接觸層，能有效降低p-BN界面的接觸電阻。

    ENGLISH ABSTRACT
    Ultraviolet (UV) light-emitting diodes (LEDs) have replaced conventional UV light sources in various applications. Nevertheless, deep-ultraviolet light-emitting diodes (DUV LEDs, λ ≤ 290nm) are still intensively investigated because of its low EQE remaining below 10% [2]. In particular, AlGaN alloys have been the most common material for DUV LEDs. In spite of continuous efforts to develop an AlGaN DUV LED, its EQE is still typically below 10%. The limitation roots in the low conductivity of p-AlxGa1-xN as its activation energy for Mg acceptor is very high (170meV to 510meV) [6]. The high activation energy of Mg acceptor leads to low hole injection efficiency. Among many approaches have been utilized to enhance DUV LEDs’s EQE, Boron Nitride (BN) has emerged as a promising candidate to substitute p-type AlGaN in DUV LEDs. Due to its layered structure, BN has high chemical and thermal stability. Besides that, with large bandgap (~6eV), it becomes a suitable material to be used as an electron blocking layer by causing a large conduction band offset and a smaller valence band offset with other III-V materials [8,9]. The most outstanding property of BN is the dramatic reduction of Mg acceptor energy level, which can be as low as 30meV [11]. It will subsequently lower the resistivity of the p-type BN layer and also increase the hole concentration efficiency. These advantages are expected to enhance the EQE of the DUV LEDs. To investigate the electrical property of p-BN, we tried to fabricate ohmic contact on p-BN by different metallizatione schemes, annealing conditions, contact layers. The temperature-dependence Hall effect measurements are conducted to estimate the activation energy of acceptors of p-type GaN, with the attempt to attain similar results from p-BN. Our studies showed that the growth pressure of the InGaN contact layer plays an important role on the contact check resistance of the Au/Ni/p-BN interface.

    TABLE OF CONTENTS CHINESE ABSTRACT i ENGLISH ABSTRACT ii ACKNOWLEDGEMENT iii TABLE OF CONTENTS iv LIST OF FIGURES vi LIST OF TABLES viii EXPLANATION OF ABBREVIATIONS ix Chapter 1 INTRODUCTION 1 1.1. Motivation 1 1.1.1. DUV LEDs: materials and applications 1 1.1.2. The issues of AlGaN-based DUV LEDs 3 1.1.3. The potential substitute for p-type AlGaN in DUV LEDs: Boron Nitride 6 1.1.4. Motivations and thesis overview 9 1.2. Activation energy – electrical conductance factor 9 1.2.1. Intrinsic and Extrinsic semiconductor 10 1.2.2. The activation energy definition 13 1.2.3. The temperature dependence of carrier concentration of semiconductor 14 1.3. Hall effect measurement 15 1.3.1. The basic principles 15 1.3.2. Van der Pauw resistivity measurement 17 1.3.3. Temperature-dependeny Hall effect measurement 19 Chapter 2 EXPERIMENT 21 2.1. Sample preparation 21 2.1.1. Double cleaning process 21 2.1.2. Metal deposition 21 2.1.3. Annealing process 22 2.2. Measurement 22 2.2.1. Hall measurement and Access HL5500 Hall system 22 Chapter 3 RESULTS AND DISCUSSIONS 26 3.1. P-type GaN 26 3.1.1. The effect of annealing temperature 27 3.1.2. The estimation of activation energy 30 3.2. P-type BN 34 3.2.1 The effect of InGaN contact layer 35 3.2.2. The effect of other processing parameters 39 Chapter 4 CONCLUSIONS AND FUTURE WORKS 42 4.1. Conclusions 42 4.2. Future works 42 REFERENCES 43

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