Browsing by Author "CHO, AY"

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EFFECTS OF SB4/GA RATIOS ON THE ELECTRICAL-PROPERTIES OF GASB SCHOTTKY DIODES
(1992-03-15)
WANG, YH
;
HOUNG, MP
;
SZE, PW
;
CHEN, JF
;
CHO, AY
Au, Cu, Ag, and Al are deposited on Te-doped n-GaSb layers directly grown on lattice mismatched GaAs semi-insulating substrates. Sb4/Ga beam equivalent pressure ratios are found to profoundly influence the electrical properties of the Schottky diodes investigated here. The fact that both breakdown voltage and barrier height decrease with increasing Sb4/Ga ratios is attributed to the increase in surface state densities for samples grown at higher Sb4/Ga ratios. This suggestion is further confirmed by the model of surface state densities employing the relationship of barrier height to metal work function. The surface state densities are in the range of 2.3 x 10(14) to 1.2 x 10(15) states/cm2/eV corresponding to Sb4/Ga ratios of 2 to 9, respectively. X-ray rocking peaks of samples grown at various Sb4/Ga ratios, and subsequently subjected to annealing, indicate different interactions at the interfaces which might support the observations.
ELECTRICAL-PROPERTIES OF UNDOPED AND SNTE-DOPED GAXIN1-XSB MOLECULAR-BEAM-EPITAXIALLY GROWN ON GAAS
(1995-01-01)
CHEN, JF
;
JAW, SH
;
CHO, AY
;
電子物理學系
;
Department of Electrophysics
Electrical properties of undoped and SnTe-doped GaxIn1-xSb on GaAs grown by molecular beam epitaxy are studied. In the studied composition x from 0.65 to 1, source SnTe is found to be an n-type dopant. The SnTe incorporation efficiency in GaxIn1-xSb is found to have no significant difference from SnTe in GaSb. The fitted ionized impurity concentrations for GaSb increases proportionally with the sample's donor concentrations, suggesting that the charged impurities are introduced through SnTe doping. On the other hand, for GaxIn1-xSb, the fitted ionized impurity concentrations do not vary with the total donor concentration. This suggests that material inhomogeneities or imperfections in GaxIn1-xSb may be the cause of mobility values which are lower than expected. In addition, the V/III beam equivalent pressure (BEP) ratio is found to critically influence the quality of the SnTe-doped ternary layers.
HIGH-REFLECTIVITY ALAS0.52SB0.48/GAINAS(P) DISTRIBUTED BRAGG MIRROR ON INP SUBSTRATE FOR 1.3-1.55-MU-M WAVELENGTHS
(1989-08-17)
TAI, K
;
FISCHER, RJ
;
CHO, AY
;
HUANG, KF
;
交大名義發表
INTERBAND TUNNELING BETWEEN VALENCE-BAND AND CONDUCTION-BAND QUANTUM-WELLS IN A GASB/ALSB/INAS/ALSB/GASB/ALSB/INAS TRIPLE-BARRIER STRUCTURE
(1992-08-01)
CHEN, JF
;
CHO, AY
;
電子物理學系
;
Department of Electrophysics
We report on the experimental studies of an interband tunneling effect between GaSb valence-band and InAs conduction-band quantum wells in a GaSb/AlSb/InAs/AlSb/GaSb/AlSb/InAs triple-barrier interband tunneling device. Multiple negative differential resistances were observed both at room temperature and 77 K. By varying the InAs well width to adjust the alignment of the conduction-band and the valence-band quasi-bound states, we observed more than one order of magnitude variation in the peak current density, indicating a significant quantization effect. Possible current conduction mechanisms were discussed based on the dependence of the peak-current density on the InAs well width.
INVESTIGATION OF NEGATIVE DIFFERENTIAL RESISTANCE PHENOMENA IN GASB/ALSB/INAS/GASB/ALSB/INAS STRUCTURES
(1994-10-01)
WANG, YH
;
LIU, MH
;
HOUNG, MP
;
CHEN, JF
;
CHO, AY
The negative differential resistance (NDR) phenomena were observed in GaSb/AlSb/InAs/-GaSb/AlSb/InAs resonant interband tunnel structures. Electron has resonantly achieved interband tunneling through the InAs/GaSb broken-gap quantum well. The InAs well width causes significant variations of the peak current density and NDR behaviors. The peak current density varies exponentially with the AlSb barrier thickness. The multiple NDR behavior was observed with appropriate InAs well and AlSb barrier thickness, e.g., 30 angstrom thick AlSb barrier and 240 angstrom wide InAs well. Only single negative resistance has, otherwise, been seen. The three-band model was used to interpret the effect of the InAs well and AlSb barrier on the current-voltage characteristics of GaSb/AlSb/InAs/GaSb/AlSb/InAs structures.
MOLECULAR-BEAM EPITAXY GROWTH OF INAS-ALSB-GASB INTERBAND TUNNELING DIODES
(1993-03-01)
CHEN, JF
;
CHO, AY
;
電子物理學系
;
Department of Electrophysics
This paper presents our studies of the growth of InAs/GaAs and GaSb/GaAs heterojunctions by molecular beam epitaxy and their applications in fabricating the InAs-AlSb-GaSb interband tunneling devices. The Hall effect and x-ray diffraction were used to determine the optimum growth conditions for the layers. In addition, the qualities of the InAs and GaSb epilayers, grown under their optimum conditions, were compared. The full width at half maximum (FWHM) from the x-ray diffraction for a GaSb epilayer is about 50 arcsec narrower than an InAs epilayer of the same thickness. The narrower FWHM and excellent surface morphology of the GaSb layer have led us to grow the polytype heterostructure on a p+-GaAs substrate using a p+-GaSb as the buffer layer. The polytype tunneling structures grown on GaAs substrates under these conditions show good negative differential resistance properties. Five different interband tunneling structures are compared and discussed in terms of their peak-current densities and peak-to-valley current ratios.
THE EFFECTS OF GASB/INAS BROKEN GAP ON INTERBAND TUNNELING CURRENT OF A GASB/INAS/GASB/ALSB/INAS TUNNELING STRUCTURE
(1992-05-01)
CHEN, JF
;
CHO, AY
;
電子物理學系
;
Department of Electrophysics
We propose and study a new GaSb/InAs/GaSb/AlSb/InAs broken-gap interband tunneling diode by varying the thicknesses of the InAs layer. A twice-higher peak current density and a three-times-higher peak-to-valley current ratio in the proposed structure with a 30-angstrom-thick InAs layer were observed relative to the structure with no InAs layer. This result indicates that the characteristic of the negative differential resistance can be improved simply by placing a thin effective InAs barrier on the GaSb side of the GaSb/AlSb/InAs single-barrier structure. The increase of the peak current is interpreted as the result of forming a quasi-bound state in the GaSb well. This interpretation is supported by the observation that the current-voltage characteristic of the proposed structure is similar to that of a conventional GaSb/AlSb/GaSb/AlSb/InAs double-barrier interband tunneling structure.