Browsing by Author "FENG, MS"

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A NEW FABRICATION TECHNOLOGY FOR FIELD-EMISSION TRIODES WITH EMITTER-GATE SEPARATION OF 0.18-MU-M
(1995-01-01)
WANG, CC
;
LEE, WF
;
KU, TK
;
CHEN, MS
;
FENG, MS
A new fabrication technology has been used for field-emission triodes with the emitter-gate separation as small as 0.18 mum to reduce the turn-on and anode voltages. The technology is based on the thermal oxidation of silicon and low-pressure chemical vapor deposition (LPCVD) of polycrystalline silicon, making the fabrication of a sub-half-micronmeter gate opening easy and reproducible. The entire process requires use of only one photolithography mask, and does not require advanced high-resolution photolithographic techniques. In this device, the oxidation process serves the three purposes of sharpening the emitters, defining the emitter-gate separation, and achieving a high-quality insulator. The finished devices have the emitter situated exactly at the center of the gate opening due to a self-alignment process. Furthermore, the LPCVD polysilicon film can form gate electrodes with a smooth edge and a small gate opening due to excellent step coverage.
A NEW PORTRAYAL OF OXIDATION OF UNDOPED POLYCRYSTALLINE SILICON FILMS IN A SHORT-DURATION
(1994-01-01)
WANG, PW
;
SU, HP
;
TSAI, MJ
;
HONG, G
;
FENG, MS
Both polysilicon films low-pressure chemical-vapor-deposited (LPCVD) at 625 degrees C and amorphous films deposited at 550 degrees C with subsequent annealing at 600 degrees C for 24 h to form polysilicon films were used to grow polyoxides at 850 degrees C in wet or dry oxygen. Detailed high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) studies have been performed to determine the microstructures of the polyoxide/polysilicon interface and the crystallinity of the polysilicon films. It is found that the oxidation phenomena of these two films are very different. For the recrystallized amorphous silicon specimens, the polyoxide/polysilicon interface is very flat because of the poor crystallinity and low-angle grain boundaries between the grains. On the other hand, the polyoxide/polysilicon interface is rough for the as-deposited polysilicon samples due to the distinct grain characteristics and the high-angle grain boundaries between these grains.
ANOMALOUS MOBILITY ENHANCEMENT IN HEAVILY CARBON-DOPED GAAS
(1994-05-15)
CHEN, HD
;
FENG, MS
;
LIN, KC
;
CHEN, PA
;
WU, CC
An anomalous mobility enhancement and metallic-type conductivity were observed in heavily carbon-doped GaAs grown by low-pressure metalorganic chemical vapor deposition. The 77 K mobility was slightly lower than that of 300 K for hole concentration between 1 x 10(18) and 4 x 10(18) cm-3. However, the 77 K mobility was enhanced from p > 4 X 10(18) cm-3, and the 300 K mobility slowly decreased with increasing hole concentration that ranged from 7 X 10(18) to 3 X 10(19) cm -3. As a result, the 77 K mobility was around 50%-60% greater than the 300 K mobility due to the metallic-type conductivity.
BANDGAP SHRINKAGE OF DEGENERATE P-TYPE GAAS BY PHOTOLUMINESCENCE SPECTROSCOPY
(1995-11-15)
FENG, MS
;
FANG, CSA
;
CHEN, HD
;
材料科學與工程學系
;
電控工程研究所
Photoluminescence characteristics of heavily carbon-, beryllium- and zinc-doped GaAs were studied in this investigation. The band-to-acceptor (e,A) transition was identified via various doping concentrations from 10(17) to 10(20) cm(-3) and the temperature from 20 to 300 K. As a result the (e,A) peak was found to be a dominant peak at 20 K instead of the band-to-band (B,B) peak at p> 1 x 10(19) cm(-3). The (e,A) peak was also observed at 300 K and enhanced with the increasing carrier concentration at p> 2.8 x 10(18) cm(-3). Bandgap shrinkage of these samples was qualitatively obtained. When p> 1 x 10(19) cm(-3), the impurity band merges with the valence band and the binding energy of the acceptor is equal to zero. Consequently, the bandgap can be taken as the energy between the conduction-band minimum and the top of the impurity band.
CARBON INCORPORATION DURING GROWTH OF GAAS BY TEGA-ASH3 BASE LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1993-06-01)
CHEN, HD
;
CHANG, CY
;
LIN, KC
;
CHAN, SH
;
FENG, MS
Heavily carbon-doped GaAs (1 X 10(18) approximately 1 X 10(20) cm-3) grown by low-pressure metalorganic chemical vapor deposition using triethylgallium and arsine as sources and liquid carbon-tetrachloride (CCl4) as dopant has been investigated. The carrier concentration was verified at various growth temperatures, V/III ratios, and CC]4 flow rates. Dopant concentration first increased from 550-degrees-C and reached a maximum at 570-degrees-C growth temperature (T(g)) and then decreased monotonously. Carbon incorporation was strongly enhanced when the V/III ratio was less than 30 at T(g) = 590-degrees-C or less than 40 at T(g) = 630-degrees-C. Hole concentration increased and then decreased as CCl4 flow rate increased. Growth rate of layers decreased as growth temperature and flow rate Of CCl4 increased. The doping efficiency of epitaxial layers grown on the (100) substrate was higher than that on the 2-degrees off toward [110] misoriented substrate. Carbon-doped GaAs films had higher Hall mobility than zinc-doped GaAs films at high doping levels due to less self-compensation. The highest dopant concentration in this system was 2.3 X 10(20) cm-3 at T(g) = 580-degrees-C and V/III = 10.
CATHODOLUMINESCENT CHARACTERISTICS OF ZNGA2O4 PHOSPHOR GROWN BY RADIO-FREQUENCY MAGNETRON SPUTTERING
(1994-09-15)
HSIEH, IJ
;
CHU, KT
;
YU, CF
;
FENG, MS
;
材料科學與工程學系
Low voltage cathodoluminescent characteristics of ZnGa2O4 phosphor grown by rf magnetron sputtering have been investigated from 300 to 700 nm. The effects of substrate heating and annealing treatment on the luminescent characteristics are also studied. A blue cathodoluminescent emission peaked at 470 nm is observed. Better luminescent properties are achieved on the films which have crystal structure with a standard powder x-ray diffraction pattern of ZnGa2O4. The effect of the strength of the ligand field on the resultant energy levels for the ZnGa2O4 phosphor is investigated. Low-voltage phosphor films with excellent cathodoluminescent characteristics have been successfully developed in this research.
CHARACTERISTICS OF POLYCRYSTALLINE SILICON THIN-FILM TRANSISTORS WITH THIN OXIDE NITRIDE GATE STRUCTURES
(1993-08-01)
CHENG, HC
;
TAI, YH
;
FENG, MS
;
WANG, JJ
;
材料科學與工程學系
Polycrystalline silicon (poly-Si) thin-film transistors (TFTs) with thin oxide/nitride (O/N) structures as gate dielectrics are fabricated. Various gate dielectrics, i.e., high-temperature thermal oxides with different thicknesses, low-pressure chemical-vapor-deposited silicon nitrides, and different combinations of O/N structures with various thicknesses, are performed to study their effects on poly-Si TFTs. The effective carrier mobility of devices with thin gate oxides is several times larger than of those with thick gate oxides. However, the breakdown voltages of thin gate oxides are too low to satisfy the requirements of TFT applications. Silicon nitrides can be substituted because of the high breakdown voltage and the smooth dielectric/poly-Si interfaces. A problem in adopting silicon nitride is the large interface stress between the silicon nitride and the poly-Si. A thin thermal pad oxide beneath the silicon nitride is therefore grown to reduce the high interface stress. Finally, the equivalent oxide thickness effect of the O/N gate structures on the electrical characteristics of TFTs is systematically investigated.
CHARACTERIZATION OF H-2/N-2 PLASMA PASSIVATION PROCESS FOR POLY-SI THIN-FILM TRANSISTORS (TFTS)
(1995-06-01)
TSAI, MJ
;
WANG, FS
;
CHENG, KL
;
WANG, SY
;
FENG, MS
The effects of nitrogen additives on the plasma hydrogenation of polycrystalline silicon thin film transistors (poly-Si TFTs) have been investigated with various radio-frequency (RF) power densities, substrate heating temperature, gas flow rates, as well as chamber pressures. The nitrogen-containing hydrogen (H-2/N-2) plasma treatments show better passivation effects on the electrical characteristics of the poly-Si TFTs than the pure H-2 hydrogenation. It is attributed to the passivation effect of the nitrogen radicals themselves and the promotion of the hydrogen plasma generation due to the radical collision. The passivation effects have been enhanced by properly chosen RF power density, gas flow rate and chamber pressure. Furthermore, the H-2/N-2 plasma were also utilized to passivate the poly-Si TFTs with different grain structures.
DOPING OF INGAP EPITAXIAL LAYERS GROWN BY LOW-PRESSURE METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION
(1993-06-20)
WU, CC
;
LIN, KC
;
CHAN, SH
;
FENG, MS
;
CHANG, CY
DEZn and H2Se were utilized as p- and n-type dopant sources for the growth in InGaP layers by low pressure metal-organic chemical vapor deposition (LP-MOCVD). The decrease in intensity of the extra spots of electron diffraction indicates that disordering is induced by the zinc doping. Streaky and wavy diffraction patterns demonstrate the formation of anti-phase domains caused by the Se dopant incorporation. The growth rate of the grown layer is reduced by more than 10% owing to the dopant incorporation. A photoluminescence emission energy difference of 141 meV between undoped and Zn-doped (5.8 x 10(18) cm-3) InGaP was obtained. The effects of doping on disordering, degeneracy of quasi-Fermi level and lattice constant reduction of grown layers were included in this study.
EFFECTS OF COLUMN-III ALKYL SOURCES ON DEEP LEVELS IN GAN GROWN BY ORGANOMETALLIC VAPOR-PHASE EPITAXY
(1995-09-18)
LEE, WI
;
HUANG, TC
;
GUO, JD
;
FENG, MS
;
材料科學與工程學系
Two different kinds of n-type GaN films were prepared by organometallic vapor phase epitaxy, one by using trimethylgallium (TMGa) and another by using triethylgallium (TEGa) as the alkyl source. Schottky diodes with well-behaved current-voltage and capacitance-voltage characteristics were fabricated. Deep-level transient spectroscopy studies were performed on these samples. Three distinct deep levels, labeled E1, E2, and E3, were measured in the film grown with TMGa, with an activation energy of 0.14, 0.39, and 1.63 +/- 0.3 eV, respectively. Only one level, E3, was observed in the film prepared with TEGa. (C) 1995 American Institute of Physics.
EFFECTS OF COLUMN-III ALKYL SOURCES ON DEEP LEVELS IN GAN GROWN BY ORGANOMETALLIC VAPOR-PHASE EPITAXY
(1995-09-18)
LEE, WI
;
HUANG, TC
;
GUO, JD
;
FENG, MS
;
材料科學與工程學系
Two different kinds of n-type GaN films were prepared by organometallic vapor phase epitaxy, one by using trimethylgallium (TMGa) and another by using triethylgallium (TEGa) as the alkyl source. Schottky diodes with well-behaved current-voltage and capacitance-voltage characteristics were fabricated. Deep-level transient spectroscopy studies were performed on these samples. Three distinct deep levels, labeled E1, E2, and E3, were measured in the film grown with TMGa, with an activation energy of 0.14, 0.39, and 1.63 +/- 0.3 eV, respectively. Only one level, E3, was observed in the film prepared with TEGa. (C) 1995 American Institute of Physics.
EFFECTS OF POLYSILICON GATE ON CHARACTERISTICS OF ONO CAPACITORS
(1992-05-01)
FENG, MS
;
LIANG, KC
;
CHANG, CY
;
LIN, LY
;
材料科學與工程學系
Electrical characteristics of oxide/nitride/oxide(ONO) capacitors using two polysilicon gates deposited by low pressure chemical vapor deposition (LPCVD) at two different temperatures (560-degrees-C, 620-degrees-C) were investigated and compared. It was found that the quality of polysilicon is important for the electrical characteristics of ONO capacitors. The as-deposited film deposited at 560-degrees-C is amorphous, whereas the film deposited at 620-degrees-C is polycrystalline. After heat treatment, the film deposited at 560-degrees-C demonstrates a preferred orientation along (111), which is different from the (220) preferred orientation of the film deposited at 620-degrees-C. Better electrical characteristics, including lower sheet resistance, higher mobility and dopant activation were observed on the films deposited at 560-degrees-C after heat treatment. With a higher quality polysilicon gate, the electrical characteristics of ONO capacitors using a low temperature deposited polysilicon gate doped by phosphorus implantation are superior to those of ONO capacitors using a POCl3 doped low temperature (560-degrees-C) deposited gate or a POCl3 doped high temperature (620-degrees-C) deposited gate.
EFFECTS OF PRESSURE ON THE FORMATION OF PHOSPHORUS-DOPED MICROCRYSTALLINE SILICON FILMS DEPOSITED BY RADIO-FREQUENCY GLOW-DISCHARGE
(1995-05-01)
FENG, MS
;
LIANG, CW
;
材料科學與工程學系
;
電子工程學系及電子研究所
;
奈米中心
GROWTH OF ZNGA2O4 PHOSPHOR BY RADIO-FREQUENCY MAGNETRON SPUTTERING
(1994-06-01)
HSIEH, IJ
;
FENG, MS
;
KUO, KT
;
LIN, P
;
材料科學與工程學系
ZnGa2O4 films have been prepared by radio frequency (RF) magnetron sputtering at various total pressure, RF power, and substrate temperatures. Microstructure and crystallographic orientation were characterized by x-ray diffraction Surface morphologies were observed by scanning electron microscope. In addition, cathodoluminescence (CL) measurement was employed to observe the emission spectra of ZnGa2O4 films. The influences of various deposition parameters on the properties of grown films were studied. The optimum substrate deposition temperature for luminous characteristics was about 500-degrees-C in this investigation. A blue cathodoluminescent emission peaked at 470 nm was observed. Good luminescent properties were observed in the films which exhibit the standard ZnGa2O4 x-ray diffraction pattern.
IN0.49GA0.51P/GAAS HETEROSTRUCTURES GROWN BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1993-07-01)
FENG, MS
;
LIN, KC
;
WU, CC
;
CHEN, HD
;
SHANG, YC
We have successfully grown In0.49Ga0.51P/GaAs heterostructures and made InGaP-based high electron mobility transistors (HEMTs) by low-pressure metalorganic chemical vapor deposition. We have found the epitaxial layer of InGaP with a Hall mobility of 4073 cm2/V s (300 K) and the photoluminescence full width at half-maximum of 1 meV (4.2 K) for GaAs, 12 meV (4.2 K) for In0.49Ga0.51P. Zinc-induced disordering phenomenon was examined by transmission electron microscope. By Shubnikov-de Haas measurement, we demonstrated the existence of a two-dimensional electron gas in InGaP/GaAs heterojunctions. The sheet carrier concentration of 2DEG is around 8.8 X 10(11) cm-2 at 1.5 K. A HEMT device with 1 mum X 40 mum gate (pattern) shows an extrinsic transconductance of 65.5 mS/mm and an intrinsic transconductance of 266 mS/mm at 300 K.
LOW-TEMPERATURE LUMINESCENT PROPERTIES OF DEGENERATE P-TYPE GAAS GROWN BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1994-02-15)
CHEN, HD
;
FENG, MS
;
CHEN, PA
;
LIN, KC
;
WU, CC
Low-temperature (20 K) luminescent properties of heavily carbon- and zinc-doped GaAs grown by low-pressure metalorganic chemical vapor deposition were investigated. The luminescence linewidth became broader at low temperatures when p > 4 X 10(19) cm-3 due to the appearance of a shoulder peak. The main peak shifted to low energy when the dopant concentration was increased; however, the shoulder peak was at around 1.485 eV and was nearly independent of the dopant concentration. The peak of the band-to-acceptor transition occurred at low temperature and dominated the emission spectra of degenerate GaAs. The peak energy of Zn-doped samples was lower than that of C-doped samples because of the existence of defects. The excitation power intensity was varied to investigate the behavior of the shoulder peak for both types of dopants. The shoulder peak was a part of the main peak because of the recombination between the conduction band and the bottom of the impurity band.
PHOTOLUMINESCENCE OF HEAVILY P-TYPE-DOPED GAAS - TEMPERATURE AND CONCENTRATION DEPENDENCES
(1994-04-01)
CHEN, HD
;
FENG, MS
;
CHEN, PA
;
LIN, KC
;
WU, JW
Photoluminescent (PL) properties of heavily carbon- and zinc-doped GaAs were investigated for concentration from 8 X 10(17) to 2.3 x 10(20) cm-3 and temperature from 300 K to 20 K. Both a band-to-band (B, B) peak and a band-to-acceptor (e, A) peak appeared at 300 K for the heavily p-type-doped GaAs PL spectra, even in degenerated GaAs. The variation of the intensities of the (e, A) peak and (B, B) peak with concentration and temperature was investigated, and the change in position of the two peaks at various concentrations and temperatures was observed. The rapid increase in linewidth with increasing concentration due to the appearance of a shoulder peak was also studied; this behavior is different from that of the shoulder peak in the PL spectrum from Zn-doped crystal.
RADIATIVE RECOMBINATION MECHANISMS OF GAAS1-XPX
(1991-12-01)
FENG, MS
;
HSIAO, HL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Dependence of excitation density and temperature of photoluminescence have been used to identify the radiative transitions of GaAs1-xPx in the indirect band-gap region (x = 0.85). At 16 K the spectra consisting of five recombination bands are observed from nitrogen-doped GaAsP. The transitions associated with nitrogen are found to dominate the recombination spectra. One of them is attributed to the recombination of excitons bound to isolated nitrogen atoms (Nx), another one is due to LO-phonon assisted transitions of Nx, and the other three are owing to donor-acceptor (D-A) and nitrogen pair transitions (NN). By combining the results of the excitation density and temperature dependence of the photoluminescence properties, the transition mechanisms for the luminescence are presented and discussed.
RAMAN-SCATTERING OF SE-DOPED GALLIUM NITRIDE FILMS
(1995-10-01)
KUO, HR
;
FENG, MS
;
GUO, JD
;
LEE, MC
;
材料科學與工程學系
Raman spectra of Se-doped gallium nitride films have been measured for the first time with good resolution and a wide range of excitation wavelengths. The signals from both buffer layer and epilayer are identified unambiguously. We have observed not only the resonant scattering related to the transition below the band gap but also the phonon-plasmon coupling due to the doping effect. The carrier concentration obtained from lineshape fitting is consistent with that from Hall measurements. By comparing the Raman shifts with those of other nitrides and gallium compounds, we found that most of them are almost linearly proportional to the square root of reciprocal masses. The bonding strengths are thus inferred from the slopes.
SE-DOPED GAN FILMS GROWN BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1995-10-01)
GUO, JD
;
FENG, MS
;
PAN, FM
;
材料科學與工程學系
;
電子工程學系及電子研究所
Se-doped GaN films are grown for the first time by low-pressure metalorganic chemical vapor deposition (LP-MOCVD), in which H2Se is used as the Se source sas. Effects of Se doping on electrical properties of GaN films are reported. Se atoms tend to out-diffuse to the surface of the GaN film at high tempi rature. The N atomic percentage is influenced by the incorporation of H2Se in the MOCVD process. The carrier concentration was found to be significantly affected by the surface defects which develop at high H2Se dosages. The highest free electron concentration obtained is about 1.5 x 10(18) cm(-3). Increasing the growth temperature from 1000 degrees C to 1050 degrees C reduces the maximum carrier concentration to about 7x10(17) cm(-3).