InAs Inserted Channel hemt 2003-21667 mdcl



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InAs Inserted Channel HEMT

  • 2003-21667

  • MDCL

  • 이 종 원


Contents

  • I. Introduction

  • II. The Design of Subchannel of InAs

  • III. Normal VS Inverted HEMT

  • IV. AlSb/InAs HEMT Growth on S.I. GaAs



Overview of InGaAs HEMT

  • Advantage for use in low noise and high frequency device

  • their high electron mobility & high sheet carrier density & high saturation drift velocity if the InAlAs/InGaAs 2DEG system

  • Conventional InP HEMT structure : high contact and gate electrode can cause large parasitic source and drain resistances (by the large conductance band discontinuity between the InGaAs cap layer and InAlAs layer, forming a barrier in the current flow between these layers)



I. Introduction

  • Why?

  • I. Superior to GaAs or InGaAs channel devices

  • a) their low-field mobility

  • b) higher-lying satellite valleys

  • c) deeper quantum well depth

  • d) higher overshoot velocity

  • II. Scaling Factor (for sub 0.1um device)

  • As Lg decreases, an appropriate aspect ratio has to be maintained to alleviate short channel Effect.

  • Also, Channel thickness has to be reduced for proper aspect ratio (∵ The thinning of barrier layer is limited by current tunneling)

  • Disadvantage ( Reducing of sheet carrier density in a channel and Undesired scattering phenomena because of hetero-junction interface and the enhancement of ionized dopant in supply layer)



InAs Inserted Channel HEMT

  • Conventional InP HEMT vs InAs Inserted HEMT (Ref. 1)



Carrier Transport Characteristic

  • (Ref. 6)



Issue of the InAs Inserted HEMT

  • I. The Design of Subchannel of InAs for composite channel

  • (dependence of a) Temperature & Thickness

  • b) Enhancement of carrier transport )

  • II. The Normal and Inverted HEMT Structure

  • III. AlSb/InAs HEMT (The Growth on S.I GaAs )



Physics

  • The Basic Idea of Composite Channel

  • Low field channel region

  • => electrons are mostly located in the high-mobility, small bandgap InGaAs layer

  • High field channel region

  • => The energy of the electrons increases and more and more electrons populate the InP layer

  • => Because of the larger bandgap, the rate of impact ionization in InP is smaller compared to that in the InGaAs channel

  • => While the low-field mobility of InP is smaller than that of InGaAs, the high-field transport properties, especially the saturation velocity, are better in InP



Physics

  • Band Structure Calculation and Electron Transport (Ref.2)

  • Γ-valley mass of strained InAs (parallel

  • => The strain brings about an increase of the InAs band gap of 0.12eV



Physics

  • Monte Carlo Simulation

  • Include polar optical phonon scattering and inter-valley deformation potential scattering at 300K

  • 26% enhancement

  • 16% enhancement



II. The Design of Subchannel

  • (Ref.3)

  • a) Mobility tested the function of Z and Lw

  • b) This test’s result is Z=3nm and Lw=4nm (Consideration of Carrier Modulation and Short Channel Effect) => 13000cm2/Vs



II. The Design of Subchannel

  • The Thickness of InAs Inserted HEMT (Another Test) (Ref. 4)

  • Double Sided Delta-doping을 이용 (for low output conductance and kink-free I/V Characteristic)



II. The Design of Subchannel

  • Design Issue (Ref.5)

  • 3.5% lattice mismatch of InAs on InP



II. The Design of Subchannel

  • AlAs/InAs Superlattice Structure (Channel Composition Modulation Transistor) (Ref. 7)

  • For high electron sheet carrier density and good carrier confinement and high electron transport

  • To improve the thermal stability of InP HEMT



III. Normal VS Inverted HEMT

  • (Ref. 8)

  • a) Normal InAs Inserted Channel HEMT : high output conductance and low breakdown voltage

  • InAs Inserted Channel Inverted HEMT : channel layer located on the carrier supply layer => low output conductance (∵ superior to electron confinement and smaller distance between gate and channel)

  • C) Little kink-effect and a high breakdown voltage



III. Normal VS Inverted HEMT

  • The enhancement of mobility characteristic

  • The scattering cased by ionized donor and interface roughness



AlSb/InAs HEMT

  • (ref. 9)

  • a) For high speed and low bias application

  • (∵ high electron mobility and velocity, high sheet charge density and good carrier confinement)

  • b) Disadvantage : charge control problem associated with impact ionization in the InAs channel (will increase as the Lg is reduced due to the higher fields present)



IV. AlSb/InAs HEMT

  • Lattice Matched System (Ref. 10)

  • I. Current Status

  • 1. Epitaxial Growth

  • Buffer (interface roughness scattering)

  • 2. Impact Ionization Effect

  • a) dominant for short gate-length when the drain bias exceeds the energy bandgap in the channel

  • => Thinner channel scheme (kink effect and low output conductance, transconductance and peak current density)

  • need for trade-off of channel thickness and device performance.



IV. AlSb/InAs HEMT

  • 개선방안

  • a. Need a good buffer for good surface morphology and good carrier transport characteristic

  • b. Thin InAs channel thickness



Conclusion

  • I. Design of Subchannel Band

  • a. InAs thickness for high speed and carrier confinement

  • b. for better performance high sheet carrier density and mobility and carrier confinement (In0.8Ga0.2As/InAs/In0.8Ga0.2As channel)

  • ∵ 3.5 % InAs mismatch in the channel

  • For Low kink effect and high breakdown voltage and the improvement of carrier mobility and sheet carrier density

  • => Inverted HEMT

  • III. For low cost and similar bandgap engineering compared with InP HEMT

  • => AlSb/InAs HEMT



InAs Inserted HEMT

  • Reference

  • 1. Modern Microwave Transistors theory, Design, and performance

  • Frank Schwierz Juin J. Liou Wiley-Interscience

  • 2. First principles band structure calculation and electron transport for strained InAs Hori, Y.; Miyamoto, Y.; Ando, Y.; Sugino, O.; Indium Phosphide and Related Materials, 1998 International Conference on , 11-15 May 1998 Pages:104 - 107

  • 3. Improved InAlAs/InGaAs HEMT characteristics by inserting an InAs layer into the InGaAs channel Akazaki, T.; Arai, K.; Enoki, T.; Ishii, Y.; Electron Device Letters, IEEE , Volume: 13 , Issue: 6 , June 1992 Pages:325 - 327

  • 4. MBE growth of double-sided doped InAlAs/InGaAs HEMTs with an InAs layer inserted in the channel  • ARTICLE Journal of Crystal Growth, Volumes 175-176, Part 2, 1 May 1997, Pages 915-918 M. Sexl, G. Böhm, D. Xu, H. Heiß, S. Kraus, G. Tränkle and G. Weimann

  • 5. Impact of subchannel design on DC and RF performance of 0.1 μm MODFETs with InAs-inserted channel Xu, D.; Osaka, J.; Suemitsu, T.; Umeda, Y.; Yamane, Y.; Ishii, Y.; Electronics Letters , Volume: 34 , Issue: 20 , 1 Oct. 1998 Pages:1976 - 1977

  • 6. High electron mobility 18,300 cm2/V·s InAlAs/InGaAs pseudomorphic structure by channel indium composition modulation Nakayama, T.; Miyamoto, H.; Oishi, E.; Samoto, N.; Indium Phosphide and Related Materials, 1995. Conference Proceedings., Seventh International Conference on , 9-13 May 1995 Pages:733 - 736



InAs Inserted Channel HEMT

  • 7. InAlAs/InGaAs channel composition modulated transistors with InAs channel and AlAs/InAs superlattice barrier layer Onda, K.; Fujihara, A.; Wakejima, A.; Mizuki, E.; Nakayama, T.; Miyamoto, H.; Ando, Y.; Kanamori, M.; Electron Device Letters, IEEE , Volume: 19 , Issue: 8 , Aug. 1998 Pages:300 - 302

  • 8. Improving the characteristic of an InAlAs/InGaAs Inverted HEMT by inserting an InAs layer into the InGaAs channel

  • Solid State Electronics vol. 38 NO. 5 pp997-1000 1995

  • Tatsushi Akazaki, Tatamoto Enoki, Kunihiro Arai and Yasunobu Ishi

  • 9. 0.1um AlSb/InAs HEMTs with InAs subchannel

  • Electronics Letters 23rd July 1998 Vol. 34 No.15

  • J.B boos, M.J. Yang, B.R. Bennett, D. Park, W. Kruppa, C.H. Yang and R. Bass

  • 10. InAs channel HFETs: current status and future trends Bolognesi, C.R.; Signals, Systems, and Electronics, 1998. ISSSE 98. 1998 URSI International Symposium on , 29 Sept.-2 Oct. 1998 Pages:56 - 61



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