Electric properties of holes in narrow channels of Si/SiGe heterostructures

L. C. Lia(李良箴 ), W. H. Hsiehb(謝文興 ), H.H. Chengc(鄭鴻祥 ),C. H. Kuanb(管傑雄 ), and Y. W. Suena(孫允武 )

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.c.Condensed Matter Science Center, National Taiwan University, Taipei, Taiwan, R.O.C.

Outline

Introduction Samples Process Results & Discussion Conclusion & Future work References

Introduction

Recently, quantum-ballistic transport in N-type Si/SiGe Heterostructure Has been investigated. The mobility is around several 105 cm2/Vs at 1.2K.[1],[2]

Generating nanostructure in the p-type Si/SiGe heterostructure

The mobility of samples we use is around several 103 cm2/Vs at 10K

Samples

N383

Samples

N384

Samples

N492

Samples

N384

δ-doping(B): 1.6×1012cm-2

5kΩ-Si substrate

500 Å Si

200 Å_strained Sispacer_layer

300Å Si0.8Ge0.2

3000Å Si buffer

Process

Lithography1.Ohmic Contact

Coating Al 1000 AAnnealing 470 C/15min

2.MesaEtching Solution: HF:HNO3:CH3COOH=1:6:2[4]

3.Metal GateCoating Ti/Al: 100A/500A

Process

E-beam LithographyPMMA

E-beam Writing by NPGS

Development Etching:

KOH:H2O=1:4[4]

Coating: Ti/AuLift Off

Results & Discussion

Quantum Point Contact Device

Results & Discussion

Unfortunately, we did not get what we expect.

Below 77K, the device does not work. Problems: 1.Stress?

2.Damage of structure?3.Etching process?

Results & Discussion

Damage of device

Conclusion & Future work

More Investigations of process:1.Etching SolutionICPRIE?

2.Where does the stress come from?strained-Si? -doping Boron?3.Traditional hall pattern does not work?

Device measurement Saw as a detector

References

Ballistic transport in an etch-defined Si/SiGe quantum point contact, U. Wiesera, U. Kunze, K. Ismail, and J. O. Chu, Applied Physics Letter Vol.81, No.9 26 Aug. 2002

Fabrication of Si/SiGe quantum point contacts by electron-beam lithography and shallow wet-chemical etching, U. Wiesera, U. Kunze, K. Ismail, and J. O. Chu, Physica E 13 (2002) 1047 – 1050

Low-dimensional inverted Si/SiGe modulation-doped electron gases using selective ex-suti ion implantation, D.J. Paul, A. Ahmed, A.C. Churchill, D.J. Robbins, and W.Y. Leong, reference paper of Cavendish Laboratory, University of Cambridge, Cambridge, UK

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