1. 140.120.11.120 1 High-frequency transport properties of two- dimensional electronic systems at low temperatures Y. W. Suen a ( 孫允武 ), W. H. Hsieh b ( 謝文興 ), L. C. Li a ( 李良箴 ), H. M. Cheng a ( 鄭憲明 ), T. C. Wan a ( 萬德昌 ), J. Y. Ou a ( 歐俊裕 ), Y. J. Huang a ( 黃盈傑 ), C. Y. Chen a ( 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

2. 140.120.11.120 2 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

3. 140.120.11.120 3

4. 4 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

5. 140.120.11.120 5 Detection by Phase Lock Loop (PLL) Type-II PLL Sample under detection phase=  1 =  1 1 PLL system  s =  s s  0 =  1 +  s =  1 1 +  s (B) s  0 =0 =  1 +   s (B) =  1 1 +  s (B) s B:the parameter (magnetic field) changed in the experiment  :velocity of the wave  can be measured very accurately. sample

6. 140.120.11.120 6 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

7. 140.120.11.120 7 SAW Delay-Line Sensor L GaAs:3.6×10 -7  -1 GaAs/LiNO 3 (Y-Z):1.8×10 -6  -1

8. 140.120.11.120 8 slower To get the same wave length (SAW), thus the same phase, one must decrease f.

9. 140.120.11.120 9 B B  f/f0f/f0 SAW Delay-Line Sensor B P SAW f/f0f/f0

10. 140.120.11.120 10 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.

11. 140.120.11.120 11 Coplanar Waveguide (CPW) Sensor Electric field 50  meandering CPW total length s

12. 140.120.11.120 12 Coplanar Waveguide (CPW) Sensor Some formulae: or

13. 140.120.11.120 13 Pulsed RF/Microwave PLL and Gated Averaging System 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.

14. 140.120.11.120 14 An improved homodyne amplitude detection scheme. 0º0º90º Ref. Signal Signal from the sample 90º hybrid Power splitter mixer To PLL To amplitude detection ~0 A home-made vector meter??

15. 140.120.11.120 15 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) s1(t)s1(t) time delay s 2 (t) signal of mixer or power detector sampling delay set by pulse generator sampling gate set by a pulse generator fed into the controlling node of a sample-and-hold circuit s3(t)s3(t) Direct coupled EM Reflected signals s 4 (t) signal after SH Peak power about –30dBm fed into lock-in

16. 140.120.11.120 16 Our system is working------

17. 140.120.11.120 17 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

18. 140.120.11.120 18 Transmission of the SAW transducers =29  m 500  m 30 pairs Y-cut Z- propagation Room temperature

19. 140.120.11.120 19 Data read from SAW delay line (sample #1): =1 =2 n s =1.9×10 11 cm -2 f 0 =120MHz T=0.3K GaAs/AlGaAs 2DES

20. 140.120.11.120 20 Data read from SAW delay line (sample #2): n s =2.5×10 11 cm -2 f 0 =120MHz T=0.3K GaAs/AlGaAs 2DES

21. 140.120.11.120 21 Compared with :(SAW Data #1)  xx of sample #1 T=0.3 K

22. 140.120.11.120 22 Compared with :(SAW Data #1)

23. 140.120.11.120 23 Compared with:(SAW Data #1)

24. 140.120.11.120 24 Transmission of the CPW transducer on Si/SiGe Width ＝ 25 μ m Gap(d eff ) ＝ 43 μ m Transmission lenth = 13mm 5k  -Si substrate 500Å Si 3000 Å Si 1.6×1012 cm-2(B doping) 100 Å_Si spacer_layer 300Å SiGe 3000Å Si buffer

25. 140.120.11.120 25 Data read from CPW:

26. 140.120.11.120 26 Compared with :

27. 140.120.11.120 27 So-Called Flows of MW modules, Graduate students, ……….. Phys. Rev.

28. 140.120.11.120 28

29. 140.120.11.120 29 1. <1  m e-beam writer UnderConstruction ^0^ 2. Acoustoelectric effect V or A Nano….. Nano….. Nano….. Nano….. Nano….. 3. Quantum dots, spins, spintronics spins 4. Replace diode detector with……(homodyne det.)