Browsing by Author "Lee, WN"

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Effect of substrate orientation on arsenic precipitation in low-temperature-grown GaAs
(2005-09-01)
Lee, WN
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Chen, YF
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Huang, JH
;
Guo, XJ
;
Kuo, CT
Arsenic precipitation in "superlattice" structures of alternately undoped and [Si] = 3 x 10(18) cm(-3)-doped GaAs grown at 250 degrees C on (100), (311)A, and (311)B GaAs substrates has been studied using transmission electron microscopy. It is found that upon postgrowth annealing at 800 degrees C, As precipitates are nearly confined in the Si-doped regions, forming two-dimensional cluster arrays located approximately at the center of each Si-doped layer. The results also show that the As precipitates in the (311)B substrate are slightly denser and larger than those in the (311)A substrate and both are markedly denser and larger than those in the (100) substrate. This can be attributed to the varying excess arsenic incorporations in differently orientated substrates.
Effects of annealing on magnetic properties of new ferromagnetic semiconductor (In, Al, Mn) As
(2005-10-01)
Chen, YF
;
Lee, WN
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Huang, JH
;
Chin, TS
;
Guo, XJ
The effects of low-temperature (210 degrees C-290 degrees C) annealing on the microstructure, lattice constant, and magnetic properties of (In0.52Al0.48)(0.91)Mn0.09As grown by low-temperature molecular-beam epitaxy were studied. The results show that low-temperature annealing has little influence on the crystalline structure and interface quality Of (In0.52Al0.48)(0.91)Mn0.09As epilayer. In contrast, both the lattice constant and Curie temperature of (In0.52Al0.48)(0.91)Mn0.09As are found to be strongly dependent on the annealing temperature. The lattice constant linearly decreases with increasing annealing temperature; while the Curie temperature increases with increasing annealing temperature up to 250 degrees C, and then abruptly decreases upon further annealed at 270 degrees C and 290 degrees C.
Effects of doping type and concentration on precipitation of nanometer arsenic clusters in low-temperature-grown GaAs
(2005-11-01)
Lee, WN
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Chen, YF
;
Huang, JH
;
Guo, XJ
;
Kuo, CT
In this study, the effects of doping type and concentration on arsenic precipitation in low-temperature-grown GaAs upon postgrowth annealing at 600, 700. and 800 degrees C were investigated. Three undoped/Si-doped/undoped (i-n-i) regions and three undoped/Be-doped/ undoped (i-p-i) regions were grown by low-temperature Molecular beam epitaxy, The results show that arsenic precipitation is dependent on doping type and doping concentration. Arsenic depletion was observed in all Be-doped layers for all annealing temperatures. However, a "dual" arsenic precipitation behavior was observed in Si-doped layers: As accumulates in [Si]=2 X 10(18) cm(-3) doped layers, while it depletes in [Si]=2 X 10(16) and 2 X 10(17) cm(-3) doped layers, We attribute this "dual" As precipitation phenomenon in Si-doped layers to the different depletion depths. (c) 2005 American Vacuum Society.
(In0.52Al0.48)(1-x)MnxAs muted magnetic semiconductor grown on InP substrates
(2006-01-11)
Lee, WN
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Chen, YF
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Huang, JH
;
Guo, XJ
;
Kuo, CT
A series of diluted magnetic semiconductors, (In0.52Al0.48)(1-x)MnxAs (0 < x <= 0. 11), was successfully grown on InP substrate by low-temperature molecular beam epitaxy. Our results indicate that (In0.52Al0.48)(1-x)MnxAs exhibits interesting magnetic behaviours at 5 K: it shows paramagnetic-like behaviour when x <= 0.05 and ferromagnetic behaviour when x >= 0.06.
MBE growth and structural and magnetic properties of (In1-gamma Al gamma)(1-x)MnxAs-diluted magnetic semiconductors
(2006-04-01)
Lee, WN
;
Chen, YF
;
Huang, JH
;
Guo, XJ
;
Kuo, CT
A series of quaternary-diluted magnetic semiconductors, (In1-y,Al-y)(1-x)MnxAs, have been successfully grown on InP substrates by low-temperature molecular beam epitaxy. The (ln(0.52)Al(0.48))(1-x)MnxAs with x <= 0.11 were grown on a nearly lattice-matched In0.52Al0.48As buffer, while the (In1-y,Al-y)(1-x)MnxAs with a higher Mn content of 0.11 < x <= 0.18 were grown on a graded 3-layer In,-,,Al-y 'As buffer structure. The results of transmission electron microscopy and double-crystal X-ray diffraction reveal that all (In1-yAly)(1-x),Mn,As epilayers are single crystal with zincblende structure, and the lattice constant increases with increasing the Mn content. The magnetic measurements show that the (In1-y,Al-y)(1-x)MnxAs semiconductors exhibit a paramagnetic-like state for x <= 0.05 while a ferromagnetic state for x >= 0.05, and the Curie temperature of ferromagnetic (In1-yAly)(1-x) MnxAs increases with increasing Mn content. (c) 2006 Elsevier B.V. All rights reserved.