Microwave Devices - Microwave Semiconductor Devices - 3 2008 / 1 학기 서 광 석

Microwave Diodes Diodes for Signal Processing - Predistorter for linear amp. - Mixer/Frequency Multiplier - Switch Schottky Diode PIN Diode Heterostructure Barrier Diode Planar-Doped Barrier Diode Diodes for Signal Sources (Oscillators) Gunn Diode IMPATT Diode Resonant Tunneling Diode Varactor Diode

Diode Nonlinear Microwave Circuits diode frequency multiplier single-ended diode mixer

Schottky Diode Metal (Schottky Contact) n GaAs (Ref.) 1. Sze, “Physics of Semiconductor Devices,” Chap. 5 2. Rhoderick, “Metal-Semiconductor Contacts” n+ GaAs Metal (Ohmic Contact) Vacuum level metal n GaAs

Schottky Diode의 Band Diagram X <Forward bias> <Zero bias> e e e e e e <Reverse bias> Small Leakage (~nA)

Schottky diode의 I-V 특성  thermionic theory holds when * thermionic emission theory : 일반적(GaAs, Si) E JSM N(E) WD <Forward bias> = effective Richardson constant (A* : include quantum mechanical correction)  thermionic theory holds when

Schottky Effect ~ 수십 mV 측정 방법 I-V 특성 C-V 특성 (Photo-electron을 이용한 측정)

Schottky Diode의 구조  GaAs의 Bn : 0.7~0.8 eV  AlxGa1-xAs 의 Bn : 0.8~0.9 eV  In0.53Ga0.47As 의 Bn : 0.2 eV (better for ohmic) In0.52Al0.48As 의 Bn : ~0.5 eV (증가 시킬 필요가 있음.) * damage free process에 의한 qBn= q(m-  ) 를 구현하기 위한 연구가 진행.  electrochemical plating에 의한 InAlAs (/InGaAs)구조의 Pt Schottky diode (vertical) (horizontal) n n+ n+ Rch에 의한 series 저항 문제 Rch n S. I. Substrate

Model of Schottky Diode Rch에 의한 series 저항 문제 RON/ROFF Rseries CJ Tera-Hertz Schottky diode – diode의 width를 0.25m 정도로 감소하여 Ron + Rseries ↓, cut-off frequency ↑ (contact pad는 air-bridge로 연결)

Microwave Schottky Diode

Membrane-Type Schottky Diode for 1.5THz Frequency Source Ref. : IEEE Trans. MTT, pp. 1538, 2004

PIN Diode Switch

Principles of Transit Time Devices IMPATT ; INJ ~ 180º (IMPact ionization Avanche Transit Time) TUNNETT ; INJ ~ 90º (TUNNEel Transit Time) Ref. : IEEE Trans. MTT, pp. 760, 2002

Transit-Time Millimeter-wave Sources

Gunn Millimeter-wave Sources

Basic Operation of Resonant Tunneling Diode (RTD) 부성(–) 저항 < RTD의 양자 우물 구조 > < RTD의 I-V 특성 > 이종 접합을 이용한 나노 양자 우물 구조 전자 터널링 현상 이용 - 초고속 동작 부성 저항 특성 - 저전력, 회로의 복잡도 감소 상온 동작 가능 ** Esaki에 의해 개발(노벨상 수상:반도체의 터널효과 연구, 1973)

RTD Millimeter-wave Sources

Frequency Multiplier Millimeter-wave Sources Heterostructure Barrier Varactor (HBV) for frequency tripler & Quintupler 3W at 1.7THz with Schottky diode (2004)

보안용 탐지 시스템 테라헤르츠(THz) 탐색시스템 밀리미터파 탐색시스템 현재의 엑스레이 검색 시스템 - 작은 양의 X-ray 사용으로 인해 많은 시간 필요 테라헤르츠(THz) 탐색시스템 주파수 흡수 계수 <폭발물> 밀리미터파 탐색시스템

Terahertz and Infrared Solid State Sources Quantum Cascade Laser (QCL) No compact sources exist for the generation of the LO power at 1-10THz. Ref. : M. Tonouchi, p. 97, Nature Photonics, 2007

Power Levels for Sub-Millimeterwave Oscillators 254GHz/158μW, 346GHz/25μW Oscillator MMICs with 35nm InP HEMT (In0.75Ga0.25As channel) - NGST, 2007 p. 223, IEEE MWCL

Sub-Millimeterwave Receiver Performance FP : Fabry-Perot SHP : Sub-Harmonically Pumped 340GHz/16dB gain LNA MMICs with 35nm InP HEMT (In0.75Ga0.25As channel) - NGST, 2007

Basic Principles of SIS Mixers • SIS: superconducting tunnel junction • SIS is a “submillimeter photodiode” – One electron per photon absorbed – “photon-assisted tunneling”

Superconducting Bolometer for Terahertz Detection Cu/Nb metal stack Bolometer Array

Fermi Level Pinning Fermi Level Pinning Various Models qBn constant regardless of metal – Fermi-level pinning (Bardeen limit) Process의 영향 Metal deposition process Surface Preparation Method Thermal annealing Ref. : H. Hasegawa, IPRM 1998, p. 451

Unified Defect Model for Schottky Barrier & Surface - MBE에서의 금속막 증착 X-ray photoelectron spectroscopy 에 의해 qB 측정 Ec ~ 0.75eV Ev ~ 0.5eV n-type GaAs deposited metal(Å) 5 10 20 15 EC ( n-type GaAs) qBn p-type GaAs EFm EF EV EC OOOO ---- OOOO + + + + EFN Wsp ESA Wsn 1.42eV ~ 0.75eV ESD ~ 0.5eV p-GaAs EFP n-GaAs EN Surface of n-GaAs Surface of p-GaAs < Unified Defect Model for GaAs > * Model의 2개(+, -) level 존재는 이견이 없으나 level의 크기, 값에 대해서는 아직 논의/연구

Semi-Insulating GaAs or InP Substrate

Undoped GaAs Semi-Insulating Substrate