Browsing by Author "CHEN, HD"

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ANOMALOUS MOBILITY ENHANCEMENT IN HEAVILY CARBON-DOPED GAAS
(1994-05-15)
CHEN, HD
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FENG, MS
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LIN, KC
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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.
BACK-GATING EFFECTS ON THE GA0.1IN0.8P/INP/INGAAS HIGH-ELECTRON-MOBILITY TRANSISTOR
(1995-07-01)
LIN, KC
;
CHANG, CY
;
WU, CC
;
CHEN, HD
;
CHEN, PA
Pseudomorphic GaInP/InP/InGaAs high electron mobility transistors (HEMT) with improved Schottky contacts and excellent electrical characteristics are grown by low-pressure metal-organic chemical vapor deposition (LP-MOCVD) on the InP substrate. These HEMTs with 1.71 mu m gate length have an average extrinsic transconductance of 225 mS/mm. The back-gating effects of this device structure are investigated for the first time in this structure. Both positive and negative bias are applied to the ohmic and Schottky back-gate contacts of these devices. The positive back-gate bias has no effect on the drain current or the output transconductances of these devices. The effect of the negative back-gate bias is very similar to that when negative bias is applied on the gate of these HEMTs.
BANDGAP SHRINKAGE OF DEGENERATE P-TYPE GAAS BY PHOTOLUMINESCENCE SPECTROSCOPY
(1995-11-15)
FENG, MS
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FANG, CSA
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CHEN, HD
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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
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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.
CATION SOURCE DEPENDENCE OF GA0.5IN0.5P GROWTH-RATE BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1994-06-15)
WU, JW
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CHANG, CY
;
LIN, KC
;
CHAN, SH
;
CHEN, HD
The Ga0.5In0.5P epilayer was grown by low-pressure metalorganic chemical vapor deposition. Trimethylgallium and triethylgallium were used as the gallium source's, while trimethylindium and ethyldimethylindium were used as the indium sources. The use of triethylgallium incorporated with trimethylindium enhanced the growth rate of Ga0.5In0.5P as compared to incorporation with ethyldimethylindium. While the use of trimethylgallium incorporated with ethyldimethylindium enhanced the growth rate of Ga0.5In0.5P significantly, as compared to incorporation with trimethylindium.
IN0.49GA0.51P/GAAS HETEROSTRUCTURES GROWN BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1993-07-01)
FENG, MS
;
LIN, KC
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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
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FENG, MS
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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.
MAGNESIUM DOPING OF INGAALP GROWN BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION
(1994-09-05)
WU, CC
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CHANG, CY
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CHEN, PA
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CHEN, HD
;
LIN, KC
Bis(cyclopentadienyl) magnesium, CP2Mg, was used as a magnesium dopant in the InGaAlP layers by low-pressure metalorganic chemical vapor deposition. The hazy surface morphology of heavily doped InGaAlP layers is significantly improved by using magnesium dopant instead of the conventional zinc dopant. We demonstrate that the effective doping efficiency of magnesium is two orders of magnitude higher than that of zinc dopant in the heavily doped InGaAlP layer grown at 720-degrees-C.
PHOTOLUMINESCENCE OF HEAVILY P-TYPE-DOPED GAAS - TEMPERATURE AND CONCENTRATION DEPENDENCES
(1994-04-01)
CHEN, HD
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FENG, MS
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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.