High-speed Type-II GaAsSb/InP DHBTs for mixed-signal IC applications

Xu, Huiming

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https://hdl.handle.net/2142/72954 Copy

Description

Title

High-speed Type-II GaAsSb/InP DHBTs for mixed-signal IC applications

Author(s)

Xu, Huiming

Issue Date

2015-01-21

Director of Research (if dissertation) or Advisor (if thesis)

Feng, Milton

Doctoral Committee Chair(s)

Feng, Milton

Committee Member(s)

• Dallesasse, John
• Jin, Jianming
• Li, Xiuling

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• III-V
• Heterojunction Bipolar Transistor (HBT)
• terahertz (THz)
• GaAsSb
• Monolithic Microwave Integrated Circuit (MMIC)
• Radio Frequency (RF)
• Indium Phosphide (InP)
• High-Speed

Abstract

Heterojunction bipolar transistors (HBTs) are widely used in high-speed mixed-signal, radio frequency, and communication ICs because of their high speed, high breakdown voltage, and high efficiency capabilities compared with Si bipolar junction transistors (BJTs) and complementary metal-oxide semiconductor (CMOS) transistors. Among different HBTs, InP HBTs offer the highest frequency operation capability with reasonably high breakdown voltage. Thus, InP HBTs are becoming increasingly important for high-speed mixed-signal ICs. Depending on different heterojunction band alignments, there are mainly three types of InP HBTs, namely, InGaAs/InP single heterojunction bipolar transistor (SHBT), Type-I InGaAs/InP double heterojunction bipolar transistor (DHBT), and Type-II GaAsSb/InP DHBT. Among these three types of InP HBTs, Type-II GaAsSb/InP DHBT has the most favorable band alignment; thus it has many superiorities compared with other InP HBT technologies. The subject of this work is the design, fabrication, and characterization of Type-II GaAsSb/InP HBTs. Chapter 1 of this work gives an overview of the development of InP HBTs and relevant figures of merit for HBTs. It will also give an introduction of different Types of InP HBTs. In Chapter 2, InP HBT material structure design, device fabrication process, and scaling are discussed. In Chapter 3, the DC, RF, and nonlinearity characterization of a Type-I/II AlInP/GaAsSb/InP DHBT will be performed and compared to that of a Type-I InP/InGaAs/InP DHBT. The physical origins of nonlinearity in Type-I InP/InGaAs/InP DHBT will also be discussed in Chapter 3. Chapter 4 details the design and performance of a composition-graded AlGaAsSb base Type-II InP DHBT. Small-signal modelling and time delay analysis show that a composition-graded AlGaAsSb base can greatly reduce the base transit time and improve device RF performance. Chapter 5 details the design and performance of a doping-graded GaAsSb base Type-II GaAsSb/InP DHBT. Small-signal modelling and time delay analysis show that a doping-graded GaAsSb base can result in base transit time comparable with a composition-graded AlGaAsSb base. It is also shown that as device emitter width scales down, the emitter peripheral surface recombination current becomes a significant portion of the total base current, leading to reduced current gain. Chapter 6 discusses the development of an emitter ledge process for the doping-graded Type-II GaAsSb/InP DHBT. Compared with devices without an emitter ledge, devices with an AlInP emitter ledge have shown much lower emitter peripheral surface recombination current density. Thus, the AlInP emitter ledge can effectively suppress the emitter size effect and improve current gain. Chapter 7 gives a brief summary of this work.

Graduation Semester

2014-12

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http://hdl.handle.net/2142/72954

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Copyright 2014 Huiming Xu

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