1140.120.11.120

High-frequency transport properties of two-dimensional electronic systems at low temperatures

Y. W. Suena(孫允武 ), W. H. Hsiehb(謝文興 ), L. C. Lia(李良箴 ), H. M. Chenga (鄭憲明 ), T. C. Wana (萬德昌 ), J. Y. Oua (歐俊裕 ), Y. J. Huanga (黃盈傑 ), C. Y. Chena (陳紫瑜 )

a Department of Physics, National Chung Hsing University, Taichung, Taiwan, R.O.C.b.Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C.

Our home:140.120.11.120

2140.120.11.120

Samples:

GaAs/AlGaAs: (1) 交大電子 李建平

(2) 以色列 / 彰師物理 吳仲卿

Si/SiGe: 台大凝態中心 鄭鴻祥

Instrumentaions:

Pulsed RF/microwave PLL: 張冠英，陳家怜，王文凱，黃盈傑，李良箴

Cryogenic Systems, Wiring & Programming: 謝文興，李良箴，歐俊裕

Samples & Measurement: 萬德昌，鄭憲明，謝文興，李良箴

Cheap Labor: 陳紫瑜，歐俊裕

Money:NSC

3140.120.11.120

4140.120.11.120

Outline

1. Detection by a Phase Lock Loop

2. Surface Acoustic Wave Detector

3. Coplanar Wave Guide Detector

4. Pulsed Microwave PLL system

5. Some Preliminary Results

6. Kind of Conclusions

7. Future Works

5140.120.11.120

Detection by Phase Lock Loop (PLL)

Type-II PLL

Sample under detection

phase=1=11PLL system

s=ss

0 =1+ s =11

+s(B)s

0 =0=1+ s(B) =11+s(B)s

111

B:the parameter (magnetic field) changed in the experiment:velocity of the wave

can be measured very accurately.

sample

6140.120.11.120

Reference

From sample

Keep at a constant phase difference

Reference

From sample

Due to the change of sample conditions

Reference Tuning the frequency to match the phase

From sample

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SAW Delay-Line Sensor

2

2

00 )／(1

1

2 Mxx

effK

Lf

f

σ

2

2

SAW )/(1

/

2 Mxx

MxxeffKk

σσσσ

L

)( 210 M

GaAs:3.6×10-7 -1

GaAs/LiNO3(Y-Z):1.8×10-6 -1

2

,2, 00 fq xxxx

8140.120.11.120

slower

To get the same wave length (SAW), thus the same phase, one must decrease f.

9140.120.11.120

10-3 10-2 10-1 100 101 102 103

xx

/M

/0

B

B

f/f0

SAW Delay-Line Sensor

B

PSAW

f/f0

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Anything GOOD to use SAW detectors?!

1. No contact!

2. Short wavelength compared to EM signals at the same frequency.

3. Low energy compared to EM signals at the same wavelength.

4. We can use SAWs to detect the special length scale in the sample via the size-resonance of SAWs and the sample.

11140.120.11.120

Coplanar Waveguide (CPW) Sensor

Electric field

50 meandering CPWtotal length s

xx

0,0 qxx

m2

12

eff

D

dG

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Coplanar Waveguide (CPW) Sensor

Some formulae: 1m)()( CjGLjjj

m

F0 eff

LC ,

eff

r

C

LZ

0

00

11

m

12

12

eff

D

d

G

m

Np

2

m

rad

8

11

2

1

0

2 ln

Z

deffD

xx or 1

2/1

20

222 8

L

eff

s

Dxx Z

dfLf

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Pulsed RF/Microwave PLL and Gated Averaging System

Gated Average

Time Delay

RF or Microwave Generator

DC-Coupled Frequency Modulation (FM)

Directional Couplers

HighSpeed Diode Switch

Step Attenuator

Double-Balance Mixer

Pulse Generator

Amplifier

Power Splitter

Intensity Output

Power Detector

PLL

Integrator積分器

Precision Counter

(b1)

(I)

(C)

(M)

(D)

(E)

(P)

(G)

(H)

(s1)

(A)

(b2)

(s2)

(b3)

Stainless-StealSemirigid Coax

Stainless-StealSemirigid Coax

黑色 : 低頻訊號橙色 : 高頻訊號

(B)

Z Z

Cryogenic Environment

Impedance Match Network

Impedance Match Network

Active LDES Region

SAW Emitter IDT

SAW Receiver IDT

Sample

(F) (F)

(S)

(J)

Why pulsed?

1. Use low average power to prevent from heating

2. Use gated averaging technique to avoid direct EM interruption

3. Avoid the reflection and multiple reflection signals

What’s different from others:

We use type II PLL, home-brew sample-&-hold circuits, and cheap lock-in amplifiers.

14140.120.11.120

An improved homodyne amplitude detection scheme.

0º 90º

Ref. Signal

Signal from the sample

90º hybrid

Power splitter

mixerTo PLL

To amplitude detection

~0

A home-made vector meter??

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Signal Gating & Averaging:

RF/Microwave pulse train

3~4 ms set by lock-in amp

~200 s set by lock-in amp

0.2~2 s set by pulse shaping circuit

s1(t)

s1(t)

time delays2(t) signal of mixer or power detector

sampling delay set by pulse generator

sampling gate set by a pulse generatorfed into the controlling node of a sample-and-hold circuit

s3(t)

Direct coupled EMReflected signals

s4(t) signal after SH

Peak power about –30dBm

fed into lock-in

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Our system is working------

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A semiconductor chip attached on the SAW delay line

BeCu SR coax

IDT SAW transducer

Chip tied on the SAW delay line

He3 sample holder

5mm

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90M 100M 110M 120M 130M 140M 150M

10dB

Tra

nsm

issi

on

Frequency

LiNbO3 120M 022

Transmission of the SAW transducers

=29m

500m

30 pairs

Y-cut

Z-propagation

Room temperature

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Data read from SAW delay line (sample #1):

0 2 4 6 8 10

0

1x10-4

2x10-4

3x10-4

0.2dBm

f/f 0

B (Tesla)

f/f0

SAW Intensity

=1

=2

ns=1.9×1011 cm-2

f0=120MHzT=0.3KGaAs/AlGaAs 2DES

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Data read from SAW delay line (sample #2):

0 2 4 6 8 10 12

SAW

Int

ensi

ty

0.001%

f

/f 0

B (Tesla)

=2

=1

ns=2.5×1011 cm-2f0=120MHzT=0.3KGaAs/AlGaAs 2DES

21140.120.11.120

Compared with :(SAW Data #1)

0 2 4 6 8 10 121x10-8

1x10-7

1x10-6

1x10-5

1x10-4

xx

B (Tesla)

xx of sample #1

T=0.3 K

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Compared with :(SAW Data #1)

0 2 4 6 8 10

measured calculated

f/f 0

B(Tesla)

-0.001

0.000

0.001

0.002

0.003

0.004

0.005

0.006

0.007

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Compared with :(SAW Data #1)

0 2 4 6 8 10

Inte

nsity

B (Tesla)

measured calculated

0.2dBm

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Transmission of the CPW transducer on Si/SiGe

Width ＝ 25μmGap(deff) ＝ 43μmTransmission lenth = 13mm

108 109

CPW at 0.3K

6dB

Tra

nsm

issi

on

Frequency(Hz) 5k-Si substrate

500Å Si

 3000 Å Si

1.6×1012 cm-2(B doping)

100 Å_Sispacer_layer

300Å SiGe

 3000Å Si buffer

 

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Data read from CPW:

0 2 4 6 8 10 12

0

5x10-4

1x10-3

N383 CPWT=0.3K

f/f 0

B (Tesla)

200MHz 800MHz

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Compared with :

0 2 4 6 8 10 12

1x10-5

2x10-5

3x10-5

N383T=0.3 K

xx

(f 0)

B (Tesla)

200MHz 800MHZ

0

1x10-5

2x10-5

3x10-5

4x10-5

DC

xx (-1

)

27140.120.11.120

So-Called

Flows ofMW modules,

Graduate students,

………..

Phys. Rev.

28140.120.11.120

29140.120.11.120

1.<1m e-beam writer

UnderConstruction^0^

2. Acoustoelectric effect V or A

Nano…..Nano…..Nano…..Nano…..Nano…..Nano…..Nano…..Nano…..Nano…..Nano…..

3. Quantum dots, spins, spintronics

spins

4. Replace diode detectorwith……(homodyne det.)