臺灣博碩士論文加值系統

　　近年來隨著無線通訊的蓬勃發展，微波元件所扮演的角色愈來愈重要，而HBT更是微波電路中不可劃缺的重要元件。InGaP/GaAs HBT因其優越的能帶結構與特性，續漸取代傳統的AlGaAs/GaAs HBT。然而對於手提元件或集成電路來說，降低元件的起動電壓能減低損耗，提高電池壽命。在眾多材料中，以InGaAsN作為基極材料的DHBT是一個非常不錯的選擇。只要適當地把銦（In）與氮（N）摻雜於GaAs中，就能製造出與GaAs基板匹配的InGaAsN-based DHBT。
　　在本論文中，針對InGaP/InGaAsN/GaAs DHBT的特性與及對溫度的相關性作詳細的討論。在起動電壓方面，對三種不同基極材料（GaAs、InGaAs、InGaAsN）的DHBT作出比較。我們發現單單加入In並不能有效的降低起動電壓，只有在加入N原子後，由於能階分列的原故，起動電壓才得以大幅度的下降。元件的電流增益達到54以上，當溫度上升時，由於InGaAsN材料本身對溫度的不靈敏，增益會呈現些微的上升，這點與傳統的InGaP/GaAs或AlGaAs/GaAs HBT有很大的分別，這使得InGaAsN-based DHBT在溫度上升時能展現出較佳的穩定性。除此之外，對於元件的低頻雜訊，我們也作了深入的探討。由實驗發現，低頻雜訊來源主要是來自基極塊材本身的復合電流，這與以GaAs為基極的HBT有很大的不同。此外，我們的元件也呈現了優良的高頻特性，fT 與fMAX 均超過40GHz。最後，元件在其它特性中也有不錯的表現，這使得InGaAsN-based DHBT很有可能成為下一個世代微波電路中最重要的元件之一。

　　With the massive development of wireless communication, microwave devices play a vital role, and the heterojunction bipolar transistors are the essential devices for the microwave circuits. Based on the excellent bandgap structure and the characteristics, InGaP/GaAs HBTs gradually replace the conventional AlGaAs/GaAs HBTs. However, for the portable devices or integrated circuits, lower turn-on voltage (Von) means lower power consumption and longer battery lifetime. In the selectivity of heterojunction materials, InGaAsN-based DHBT is a suitable choice to achieve this goal. By incorporating an appropriate amount of indium and nitrogen into GaAs, a novel material InGaAsN that is lattice matched to GaAs is achieved.

　　In this thesis, the discussions are focused on the device characteristics and the temperature dependence of the device. In turn-on voltage, three different base materials (GaAs, InGaAs and InGaAsN) are compared, only incorporating indium is found to be an ineffective method to decrease the turn-on voltage. By adding a small amount of nitrogen into InGaAs, the interaction between the conduction band and a narrow resonant band formed by nitrogen states leads to a splitting of the conduction band into two subbands and a reduction of the fundamental band gap. In result, turn-on voltage dramatically decreases. In room temperature, the DC current gain is over 54. Since InGaAsN material is insensitive to temperature, the current gain increases slightly as the temperature increases. This indicated a great difference compared with the conventional InGaP/GaAs or AlGaAs/GaAs HBTs. In addition, researches also include low-frequency noise discussion. According to the experiment, it is known that the 1/f noise comes from the base bulk recombination current and differs from that of GaAs-based HBTs. The device shows excellent high frequency characteristics, both fT and fMAX are higher than 40GHz. Finally, the device shows fine performances in other characteristics, this allows the InGaAsN-based DHBT to be able to become the most important components of microwave circuits in the next generation.

Content
Abstract (in Chinese) ………………………………………… I
Abstract (in English) ………………………………………………… III
Content ………………………………………………………………… V
Figure Captions ……………………………………………………... VII
Chapter 1. Introduction ………………………………………………. 1
Chapter 2. Growth and Measurement Systems ……………………... 4
2-1 MOVPE System …………………………………………………… 4
2-2 PECVD …………………………………………………………… 8
2-3 1/f Noise Measurement System ……………………………… 9
2-4 RF Measurement System ……………………………………… 10
Chapter 3. Fabrication of Double Heterojunction Bipolar Transistors
3-1 The Structure of DHBT ……………………………………… 12
3-2 The DHBT Device Fabrication Process …………………… 12
3-2.1 Emitter Metallization ………………………………12
3-2.2 Emitter Mesa ………………………………………… 13
3-2.3 Base Metallization …………………………………13
3-2.4 Base Pedestal ……………………………………… 14
3-2.5 Collector Metallization …………………………14
3-2.6 Device Isolation ……………………………………………14
3-2.7 Insulator Layer and Via ……………………………………15
3-2.8 Pad and Interconnection ………………………………15
Chapter 4. Experimental Results and Discussions
4-1 DC Characteristics of DHBT …………………………………………… 16
4-1.1 BE and BC Junction Diodes …………………………………… 16
4-1.2 Common Emitter I-V Characteristic ………………………16
4-1.3 Current Gain Characteristics on RT & Temperature
Dependence ……………………………………………………17
4-1.4 Offset Voltage Characteristics on RT & Temperature
Dependence…………………………………………20
4-1.5 Turn-On Voltage Investigation on DHBT Structure with
Different Base Layers ………………………………………22
4-1.6 Breakdown Voltage on RT & HT ……………………………24
4-2 The Origin and Characteristics of 1/f Noise in the InGaAsN-Based
DHBT …………………………………………………………………26
4-3 Cut-off Frequency and Transit Time …………………………………30
Chapter 5. Conclusions ……………………………………………… 33
References
Figures

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