臺灣博碩士論文加值系統

本論文主要是研究及製作出高線性度及低雜訊之磷化銦鎵高電子遷移率電晶體。此元件使用磷化銦鎵為蕭特基層(Schottky layer)之材料，利用磷化銦鎵之高能間隙特性，以降低元件之漏電流及雜訊；在阻隔層(Spacer)使用砷化鋁鎵以提高元件之電子遷移率，並利用兩層矽平面摻雜方式來增加元件電流分佈之均勻性，亦使得元件具有良好之線性度。
本論文所製作出之磷化銦鎵高電子遷移率電晶體，閘極長度為0.25μm。閘極寬度為160μm之直流特性具有240 mA/mm的飽和電流密度，傳導率(Transconductance)為414.2 mS/mm，截止電壓(Pinch-off voltage)為-0.8V，閘極-汲極間的崩潰電壓為15.6V，元件之截止頻率(fT )為70 GHz，最大震盪頻率(fmax)為210 GHz；而閘極寬度為300μm之直流特性則具有226 mA/mm的飽和電流密度，傳導率為394 mS/mm，截止電壓為-0.9V，閘極-汲極間的崩潰電壓為14.4V。
此結構之元件具有低雜訊之特性，閘極寬度為160μm之元件在頻率12 GHz時最低雜訊指數(Fmin)為0.45dB，且具有良好之線性度，在頻率6 GHz偏壓點汲極-源極間電壓為2.4V時輸出三階交叉點(OIP3) 可達到28.1 dBm，而此時輸入三階交叉點(IIP3) 則為7 dBm；由此驗證，此結構之元件，為一低雜訊及高線性度之高頻元件。

The purpose of this dissertation is to develop the high linearity and low noise high electron mobility transistors for wireless application. The device structure design has the following features: First, high band-gap InGaP material was used as the Schottky layer to reduce the leakage current and noise figure of the devices. Second, AlGaAs was used as the spacer layer to increase the device electron mobility. Third, two Si δ-doped layers above and below the InGaAs channel region in the structure were used to increase the uniformity of the distribution of the electric current, and improve the linearity of the devices.
In this study, the InGaP/InGaAs PHEMT developed with gate length of 0.25μm and gate width of 160μm had the following DC characteristics: Idss=240 mA/mm, gm=414.2 mS/mm, pich-off voltage=-0.8V, and gate-to-drain breakdown voltage BVgd=15.6V. The devices also demonstrated good RF characteristics with fT=70 GHz, and fmax=210 GHz.
The devices also exhibited excellent low noise characteristics. The 160μm HEMT had a noise figure of 0.45dB at 12 GHz, and demonstrated high linearity characteristics. The OIP3 and the IIP3 at 6 GHz and bias at Vds=2.4V were 28.1 dBm and 7 dBm, respectively. From the results of the RF measurement, the PHEMT developed is a high-frequency low noise device with excellent high linearity and is applicable for high frequency wireless applications.

Chapter 1 Introduction
Chapter 2 Indices of device performance
2-1 Device model
2-2 Noise figure (NF)
2-3 Linearity
2-4 Breakdown voltage (BVgd)
2-4-1 Physics for device breakdown
2-4-2 Analytic model for design
2-4-3 Improvement of the breakdown voltage
2-5 Extrinsic transconductance (gm)
2-6 Unit current gain cut-off frequency (fT) and
maximum frequency of oscillation (fmax)
Chapter 3 Experimental
3-1 Device structure
3-2 Device fabrication process
3-2-1 Wafer cleaning
3-2-2 Device isolation
3-2-3 Ohmic contact formation
3-2-4 Recess and gate formation
3-2-5 Device passivation
3-2-6 Air-bridge plating
Chapter 4 Instruments & Measurements
4-1 Instruments
4-2 DC characteristics measurement
4-2-1 Contact properties
4-2-2 Current-voltage curves
4-2-3 Pinch-off voltage (VPO) & Breakdown
voltage (VB)
4-2-4 Extrinsic transconductance (gm)
4-3 RF characteristics measurement
4-3-1 Scattering parameters (S-parameters)
4-3-2 Noise figure (NF)
4-3-3 Third-order intercept point (IP3)
Chapter 5 Results and Discussion
5-1 DC characteristics of the InGaP PHEMTs
5-2 RF characteristics of the InGaP PHEMTs
Chapter 6 Conclusions

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