Studies on Electron Spin Relaxation in AlGaAs/GaAs Multi Quantum Wells

Wu, Yu

doi:10.4028/www.scientific.net/AMM.143-144.216

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HomeApplied Mechanics and MaterialsElectrical Information and Mechatronics and...Studies on Electron Spin Relaxation in AlGaAs/GaAs...

Studies on Electron Spin Relaxation in AlGaAs/GaAs Multi Quantum Wells

Abstract:

Time-resolved circularly polarized pump-probe spectroscopy is used to study the carrier density dependence of the electron spin polarization dynamics in AlGaAs/GaAs multi quantum wells at room temperature. Experimental results show that the spin relaxation time increases with the carrier density, which is in conformity with D'yakonov-Perel relaxation mechanism.

Info:

Periodical:

Applied Mechanics and Materials (Volumes 143-144)

Main Theme:

Electrical Information and Mechatronics and Applications

Edited by:

Xudong Wang, Baoyu Xu and Shaobo Zhong

Pages:

216-219

DOI:

https://doi.org/10.4028/www.scientific.net/AMM.143-144.216

Citation:

Y. Wu, "Studies on Electron Spin Relaxation in AlGaAs/GaAs Multi Quantum Wells", Applied Mechanics and Materials, Vols. 143-144, pp. 216-219, 2012

Online since:

December 2011

Authors:

Yu Wu

Keywords:

Electron Spin Orbit Coupling, Electron Spin Relaxation, Time Resolved Pump-Probe Spectroscopy

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References

[1] Wolf S. A., Awschalom D. D., Buhrman R. A., et al., Science, vol. 294(2001), p.1488.

[2] M. I. D'yakonov, V. I. Perel., Theory. Sov. Phys. JETP, 1974, vol. 38, pp: 177.

[3] M. I. D'yakonov, V. I. Perel, V. L. Berkovits, V. I. Safarov., Sov. Phys. JETP. 1975, vol. 40, pp: 950.

[4] M. I. D'yakonov, V. Yu. Kachorovski, Sov. Phys. Semicond , 1986, vol. 20, pp: 110.

[5] Hiltom D. J. and Tang C. L., Phys Rev Lett., 2002, 89(14): 146601.

[6] R.J. Seymour, R.R. Alfano, Appl. Phys. Lett., 1980, vol. 37, pp: 231.

[7] Tackeuchi A., Kuroda T., Muto S., Wada O., Jpn. J. Appl. Phys. , 1999, vol. 38, pp: 4680.

[8] Tackeuchi A. and Wada O, Appl. Phys. Lett., 1997, vol. 70, pp: 1131.

[9] M. I. D'yakonov, V. Yu. Kachorovski, Sov. Phys. Semicond , 1986, vol. 20, pp: 110.

[10] Ridley B. K. : Quantum processes in semiconductors , 1982, chap 4, pp: 143.

Paper TitlePages

Ultrafast Relaxation Character of Nonequilibrium Carriers in GaAs Excited by Femtosecond Laser

Authors: Ming Zhou, Dong Qing Yuan, Li Peng Liu, Hui Xia Liu, Nai Fei Ren

Abstract: Experiment setup of femtosecond laser pump probe was established, the time resolution of time-delay setting reached 67fs. By use of femtosecond laser with width of 30fs and wavelength is 796nm the dependence of transient change of reflectivity on delayed time in GaAs was measured by pump-probe method. By calculating the change of complex index of refraction (%n), free-carrier effect, lattice-temperature and carrier recombination contributions to relaxation curve was analyzed. When the carrier density N is 1.44×1018/cm3, free-carrier contribution to refraction index %nFC is -7.33×10-4, lattice-temperature %nLT is 0.85×10-4. Based on recombination rate equation, recombination lifetime of 980ps was deduced.

572

Quantitative Mobility Spectrum Analysis of AlGaN/GaN Heterostructures Using Variable-Field Hall Measurements

Authors: N. Biyikli, Cole W. Litton, J. Xie, Y.T. Moon, F. Yun, C.G. Stefanita, S. Bandyopadhyay, J.R. Meyer, Hadis Morkoç

Abstract: Carrier transport properties of AlGaN/GaN heterostructures have been analyzed with the quantitative mobility spectrum analysis (QMSA) technique. The nominally-undoped Al0.15Ga0.85N/GaN sample was grown by metal-organic vapor phase epitaxy. Variable-magneticfield Hall measurements were carried out in the temperature range of 4-160 K and magnetic field range of 0-6.6 T. QMSA was applied to the experimental variable-field data to extract the concentrations and mobilities associated with the high-mobility 2DEG and the relatively lowmobility bulk electrons for the temperature range investigated. For temperatures below 100 K the calculated mobility and carrier density values were close to the experimental results. No bulk conduction was observed in this temperature range. At 160 K, QMSA results show that parallel conduction in 3 mm thick GaN layer started to affect the average electron mobility.

1533

Optical Characterization of Defect-Related Carrier Recombination and Transport Features in GaN Substrates and CVD Diamonds

Authors: Kęstutis Jarašiūnas, T. Malinauskas, R. Aleksiejunas, Bo Monemar, V. Ralchenko, A. Gontar, E. Ivakin

Abstract: Defect related carrier recombination and transport properties have been investigated in differently doped HVPE GaN substrates and CVD diamond layers. Carrier generation by interband transitions or by deep-defect photoexcitation were realized for studies of GaN samples by using picosecond pulses at 351 nm or 527 nm. This allowed to create favorable conditions for radiative and nonradiative recombination in the crystals and reveal peculiarities of photoelectrical properties of high and low density plasma in undoped, doped, and compensated GaN. In CVD diamonds, carrier diffusion length was found equal to ~ 0.5 μm and non-dependent on nitrogen density, while the carrier lifetime varied from 0.2 to 0.6 ns.

1301

On Applicability of Time-Resolved Optical Techniques for Characterization of Differently Grown 3C-SiC Crystals and Heterostructures

Authors: Patrik Ščajev, Pavels Onufrijevs, Georgios Manolis, Mindaugas Karaliūnas, Saulius Nargelas, Nikoletta Jegenyes, Jean Lorenzzi, Gabriel Ferro, Milena Beshkova, Remigijus Vasiliauskas, Mikael Syväjärvi, Rositza Yakimova, Masashi Kato, Kęstutis Jarašiūnas

Abstract: We applied a number of time-resolved optical techniques for investigation of optical and photoelectrical properties of cubic SiC grown by different technologies on different substrates. The excess carriers were injected by a short laser pulse and their dynamics was monitored by free-carrier absorption, light-induced transient grating, and photoluminescence techniques in a wide excitation range. Combining an optical and electrical probe beam delay, we found that free carrier lifetimes in differently grown layers vary from few ns up to 20 μs. Temperature dependences of carrier diffusivity and lifetime revealed a pronounced carrier trapping in thin sublimation grown layers. In free-standing layers and thick sublimation layers, the ambipolar mobility was found the highest (120 cm²/Vs at room temperature). A linear correlation between the room-temperature band edge emission and carrier lifetime in differently grown layers was attributed to defect density, strongly dependent on the used growth conditions.

159

Electron Spin Relaxation in Semiconductor Quantum Wells

Authors: Yu Wu, Qian Shou

Abstract: The dependence of electron spin relaxation on the carrier density are investigated based on the D’yakonov-Perel relaxation mechanism. Experimental results obtained by using femtosecond pump-probe technique in AlGaAs/GaAs multiple quantum wells at room temperature show that the spin relaxation time increases from 58 to 82ps at carrier density of 1×1017 to 1×1018cm－3 consistent with the theoretical prediction. This result reveals that with the increment of the carrier density, the spin orbit interaction reduces due to the more frequent momentum scattering and the spin relaxation time prolongs

155