臺灣博碩士論文加值系統

在本論文中，我們研究以「金屬有機化學氣相沉積」方式成長三種不同元件通道結構之砷化銦鋁/砷化銦鎵/磷化銦高電子移動率電晶體，分別為均勻式通道、步階型漸變式通道、以及反向線性漸變式通道。

以磷化銦為基底之高電子移動率電晶體 (InP-based HEMT)經過證明具有高頻應用以及低雜訊的特性，但是由於存在較大閘極漏電流和較小的崩潰電壓而限制了元件在功率方面的應用，因此為了改善元件崩潰電壓特性，我們藉由有效限制通道厚度、降低閘極與通道中的電場分佈，以改善衝擊游離化的效應。另外，我們在蕭基層上成長一層磷化銦，一方面和砷化銦鋁具有高蝕刻選擇比，以獲致較高的蝕刻均勻度；另一方面也可提供防止蕭基層產生表面缺陷與有效改善紐結效應。

由實驗結果顯示，步階型漸變式通道結構可以增加元件外部轉導值、降低輸出轉導，進而得到較高電壓增益並且改善元件高頻特性，因此適合利用在高速和高增益的應用，另一方面，反向線性漸變式通道結構擁有較大閘極電壓擺幅特性，並且增加元件的電流驅動能力和崩潰電壓，可以利用在高線性度以及功率應用方面。另外，我們發現在高電子移動率電晶體中利用步階型漸變式通道、以及反向線性漸變式通道可以改善元件的熱穩定性，進而增強元件的高溫應用。

In this thesis, the characteristics of the InAlAs/InGaAs/InP HEMT with different channel structures by metal organic chemical vapor deposition (LP-MOCVD) have been studied. The channel structures were lattice-match channel, step-graded channel and inverse linear-graded channel, respectively.

InP-based HEMTs have demonstrated excellent high frequency and low noise performance. But the power performance is limited by excessive leakage currents and relatively low breakdown voltage. In order to improve the breakdown characteristics, reduction of the channel thickness effectively leads to effectively suppression of impact ionization by limiting the electric field beneath the gate. Besides, we have grown an InP layer on the InAlAs Schottky layer, the etching stop layer, which is a viable solution to improve Vth reproducibility. It also contributes to suppressing kink effects in InP-based HEMTs and avoiding surface trap generation.

From experimental results, Due to the intrinsic high-speed property of the high-In composition In0.56Ga0.44As subchannel design and the decreased separation distance between 2DEG and gate electrode, the SGC-HEMT exhibiting higher extrinsic transconductance, lower output conductance, higher voltage gain, and improved microwave performances, is suitable for high-frequency and high-gain millimeter-wave integrated circuit (MMIC) applications. On the other hand, ILGC-HEMT has demonstrated superior linearity, wider GVS regime, improved breakdown characteristics, improved current drive, and superior output power performance, due to the inverse linearly-graded InxGa1-xAs channel design. Consequently, the proposed ILGC-HEMT is suitable for high-power with good linearity MMIC applications. Besides, we also found using step-graded channel and inverse linear-graded channel structures in HEMTs can improve the thermal stability for its promising high-temperature applications.

Acknowledgement...............................................................i
Abstract (Chinese)............................................................ii
Abstract (English)..........................................................iii
Figure Captions.............................................................vii
Chapter 1 Introduction........................................................1
Chapter 2 Epitaxial Growth System and Experimental Procedures ................4
2-1 Introduction of LP-MOVCD system...........................................4
2-2 Device Fabrication Processes..............................................7
2-2-1 Sample Orienting...............................................7
2-2-2 Mesa Isolation.................................................7
2-2-3 Source and Drain Ohmic Contact Formation.......................8
2-2-4 Gate Schottky Contact Formation................................8
Chapter 3 Operation principle of InGaAs channel HEMT.........................10
3-1 Introduction ............................................................11
3-2 HEMT Structure Layer Design.........................................12
3-2-1 Cap Layer..............................................................12
3-2-2 Etching stop layer.....................................................12
3-2-3 Schottky Layer.........................................................13
3-2-4 δ-doped Carrier Supply Layer...........................................13
3-2-5 Spacer Layer...........................................................14
3-2-6 Various InxGa1-xAs channel.............................................14
3-2-7 Buffer layer...........................................................14
Chapter 4 Experimental Results and Discussions...............................16
4-1 Device Structures........................................................16
4-2 Hall Measurement.........................................................17
4-3 SIMS Measurement.........................................................18
4-4 DC Characteristics.......................................................19
4-4-1 DC Characteristics at 300 K............................................19
(A) Current-Voltage Characteristics..........................................19
(B) Extrinsic Transconductance Characteristics...............................20
(C) Two-terminal Breakdown Voltage Characteristics...........................22
4-4-2 Kink Effect............................................................23
(A) Impact Ionization........................................................23
(B) Output Conductance.......................................................24
4-4-3 Temperature Characteristics............................................25
(A) Extrinsic Transconductance Characteristics...............................25
(B) Two-terminal Breakdown Voltage Characteristics...........................27
4-5 RF Characteristics.......................................................27
4-6 Power Characteristics....................................................28
4-7 Noise Characteristics....................................................29
Chapter 5 Conclusions........................................................31
Reference....................................................................33

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