Search Results - (Author, Cooperation:W. C. Hsu)

2014-01-18

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

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2018-01-09

Nature Publishing Group (NPG)

2041-1723

Biology

Chemistry and Pharmacology

Natural Sciences in General

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2015-09-10

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

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2013-07-13

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

1089-7550

AIP Digital Archive

Physics

The electron mobility and the two-dimensional electron gas (2DEG) concentration in different indium compositions (0.1〈x〈0.6) δ-doped GaAs/InxGa1−xAs/GaAs pseudomorphic structures grown by low-pressure metalorganic chemical vapor deposition are studied. The electron mobilities of a δ-doped GaAs layer are comparable to those of previous reports. Furthermore, the maximum mobility (5500 and 33 000 cm2/V s at 300 and 77 K, respectively) of the proposed pseudomorphic structure appears at x=0.37. Taking into account of strain and quantum effects, the variation trends of calculated 2DEG concentrations are in good agreement with the experimental results.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Delta-doped (δ-doped)GaAs/In0.25Ga0.75As/GaAs strained-layer modulation-doped field-effect transistor (δ-SMODFET) structures grown by the low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technique have been studied for the first time. The δ-doped GaAs, adopted as the electron supplier, was obtained by a stop-growth process so that a very thin and heavily doped layer (1.9×1013 cm−2) can be realized. Experimental results show that a structure with an 80 A(ring) In0.25Ga0.75As layer as the active channel and an 80 A(ring) spacer layer demonstrated the highest two-dimensional electron gases mobility of 26 800 cm2/V s. This structure is easy to achieve by the LP-MOCVD method because the growth of AlGaAs is avoided and is promising for high performance FETs.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The field-dependent capture-emission process has been studied for double Poole–Frenkel well traps compared with that of single Poole–Frenkel well trap. The emission rate increases with increasing field strength for a single trap. However, for a double trap, it increases to a maximum then decreases with further increasing field due to the barrier lowering and interstate interactions between these two wells. Experimental capacitance deep-level transient spectroscopic data of GaAs samples grown by molecular-beam epitaxy show that when there is a delay in the capacitance transient then there always appear two levels, namely, 0.4 and 0.5 eV. In addition, for both levels, the emission rate increases first to a maximum and then decreases with increasing electric field.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Multiple-δ-doped GaAs field effect transistors using graded-like δ-doping profile are demonstrated and investigated. An extremely high carrier density of 1.2×1013 (7.9×1012) cm−2 along with an enhanced Hall mobility of 1700 (3300) cm2/v s at 300 (77) K for a triple-δ-doped GaAs structure are achieved. The dc characteristic reveals an extrinsic transconductance as high as 110 mS/mm at room temperature with a gate length of 2 μm. Three separated peaks in the transconductance versus gate bias curve are observed. Meanwhile, a broad and flat transconductance region is obtained. © 1995 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

In this letter a new type of GaAs/In0.25Ga0.75As/GaAs pseudomorphic single quantum well heterostructure by selectively double-δ-doping GaAs layers on both sides of the InGaAs channel grown by low-pressure metalorganic chemical vapor deposition is demonstrated. An extremely high two-dimensional electron gas concentration more than 1×1013 cm−2 with enhanced mobility of 2900 cm2/V s is achieved. This type of structure can easily break through the doping limitation in conventional heterostructures while keeping a high mobility.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

A δ-doped GaAs/graded InxGa1−xAs/GaAs pseudomorphic structure grown by low-pressure metal-organic chemical vapor deposition was demonstrated for the first time. The graded InxGa1−x As layer in which the composition x ranged from 0.25 to 0.20 was strained to obtain a pseudomorphic structure. Furthermore, a δ-doped high-electron mobility transistor( δ-HEMT) employing a graded InxGa1−x As layer was successfully fabricated. Due to better electron confinement and lower interface roughness scattering, the present structure reveals higher saturation current density, higher transconductance, and higher product of mobility and two-dimensional sheet density as compared to those of conventional HEMTs which were also fabricated by the same system and procedure.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

A δ-doped GaAs/In0.2Ga0.8As p-channel heterostructure field-effect transistor grown by low-pressure metalorganic chemical vapor deposition is demonstrated. The mobilities and two-dimensional hole gas concentrations at 300 (77) K are 260 (2600) cm2/v s and 1012 (5.5×1011) cm−2, respectively. For a gate length of 1.5 μm, the maximum extrinsic transconductances are 15 mS/mm at 300 K and 24 mS/mm at 77 K. The high transconductances extend a wide range versus gate voltage. © 1995 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We present the observation of an effective real-space transfer process of hot electrons resulting in a very strong negative differential resistance in GaAs/In0.25Ga0.75As/GaAs pseudomorphic heterostructure by growing symmetrically double δ-doping layers on both sides of the InGaAs channel. By Hall measurements, the proposed structure shows carrier mobility as high as 4500 (14 100) cm2/V s at 300 (77) K which is suitable for high-frequency operations. Meanwhile, this structure with a 5×100 μm2 emitter channel reveals extremely sharp charge injection, broad current valley range ((approximately-greater-than)3 V), high transconductance (over 23.5 S/mm), high current driving capability, and high peak-to-valley current ratio (up to 156 000). We also carried out secondary-ion mass spectrometry profiles to confirm the quality of the proposed structure. © 1995 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

A lattice-matched In0.53Al0.22Ga0.25As/InP heterojunction bipolar transistor has been fabricated by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). No potential spike due to zero conduction band discontinuity at the emitter-base heterojunction is obtained. Meanwhile, the larger valence discontinuity (ΔEV=460 meV) than AlGaAs/GaAs and InGaAs/InP systems provides this structure with a better hole confinement. An offset voltage as low as 50 mV along with a current gain of 85 is achieved. © 1995 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

A novel double δ-doped heterostructure employing symmetric graded InGaAs quantum wells as the active channel grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) has been successfully fabricated. The proposed symmetrically graded InGaAs pseudomorphic structure manifests significantly improved electron mobility as high as 5300 (26 000) cm2/V s at 300 (77) K due to superior confinement and to the lower interface roughness scattering at GaAs/InGaAs heterointerfaces. We also carried out photoluminescence (PL) spectra and secondary-ion mass spectrometry (SIMS) profiles to confirm the quality of the proposed structures.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

An In0.5(Al0.66Ga0.34)0.5P/GaAs heterostructure field-effect transistor has been fabricated by metal-organic chemical vapor deposition. A turn-on voltage as high as 3.2 V along with an extremely low gate reverse leakage current of 69 μA/mm at VGD=−40 V are achieved. In addition, it is found that the device can be operated with gate voltage up to 1.5 V without significant drain current compression. These characteristics are attributed to the use of high Schottky barrier height, high band gap of In0.5(Al0.66Ga0.34)0.5P Schottky layer, and to the large conduction-band discontinuity at the In0.5(Al0.66Ga0.34)0.5P/GaAs heterojunction. © 1999 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

A lattice-matched δ-doped In0.34Al0.66As0.85Sb0.15/InP heterostructure field-effect transistor (HFET) which provides large band gap (∼1.8 eV), high Schottky barrier height (φB〉0.73 eV), and large conduction-band discontinuity (ΔEc〉0.7 eV) has been proposed. In0.34Al0.66As0.85Sb0.15/InP heterostructures are shown to be type II heterojunctions with the staggered band lineup. This HFET demonstrates a output conductance of less than 1 mS/mm. Two-terminal gate-source breakdown voltage is more than 20 V with a leakage current as low as 170 μA at room temperature. High three-terminal off-state breakdown voltage as high as 36 V, and three-terminal on-state breakdown voltage as high as 18.6 V are achieved. The gate voltage swing is also significantly improved. © 2000 American Institute of Physics.

Electronic Resource

1750-3841

Blackwell Publishing Journal Backfiles 1879-2005

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Process Engineering, Biotechnology, Nutrition Technology

A method for estimating antioxidative potency (AOP) was achieved by incubating emulsified linoleic acid in a 1 mL iron/ascorbate system at 37 °C for 30 min followed by absorbance measurement at 234 nm to determine the conjugated diene hydroperoxide (CDHP) content. By that method, 100% AOP was obtained when 10 ppm butylated hydroxytoluene or 50 ppm α-tocopherol was introduced. When freeze-dried peanut sprouts were cooked with ground pork-fat patties and the separated oils were stored at 60 °C for CDHP determination, the highest AOP was observed in the 144 h germinated sprout roots. After extracting the sprout roots with methanol and AOP evaluation by the iron/ascorbate and pork-oil storage methods, both showed similar AOP trends as affected by extract concentration.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Significant improvement on two-dimensional electron gas (2DEG) concentration and mobility in a δ-doping superlattice GaAs/In0.25Ga0.75As/GaAs pseudomorphic heterostructures prepared by low-pressure metalorganic chemical vapor deposition have been demonstrated and discussed. The secondary-ion mass spectrometry profiles of these δ-doping superlattice structures were studied. The triple and double δ-doping superlattice heterostructures showed extremely high 2DEG concentrations of 8.8 (6.0) and 4.3 (2.5)×1012 cm−2 along with enhanced mobilities of 2710 (6500) and 3916 (18400) cm2/V s at 300 (77) K, respectively. The 2DEG concentrations, to our knowledge, are among the highest for previously reported pseudomorphic heterostructures with similar mobilities.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

A double δ-doped In0.49Ga0.51P/In0.25Ga0.75As/GaAs high electron mobility transistor has been successfully fabricated by metalorganic chemical-vapor deposition. Improved electron mobility as high as 5410 (19 200) cm2/V s at 300 (77) K along with turn-on voltage as high as 2.3 V and reverse gate-to-drain voltage up to 75 V are achieved. These characteristics are attributed to the use of the δ-doped, undoped InGaP Schottky layer, and undoped GaAs setback layer. Moreover, the parasitic parallel conduction can be eliminated. The activation energy is also deduced. © 1999 American Institute of Physics.

Electronic Resource

0014-4827

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Medicine

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