Ethyldimethylindium Research Articles

Nucleation Layer의 표면 거칠기가 GaAs 기판 위에 성장된 InP 에피층의 품질에 미치는 영향

Department of Electronic Engineering, Cheongju University, Cheongju 360-764, Korea(Received July 4, 2012; Revised July 11, 2012; Accepted July 12, 2012)Abstract: Heteroepitaxial InP films have been grown on GaAs substrates to study the effects of the nucleation layer's surface roughness on the epitaxial layer's quality. For this, InP nucleation layers were grown at 400℃ with various ethyldimethylindium (EDMIn) flow rates and durations of growth, annealed at 620℃ for 10 minutes and then InP epitaxial layers were grown at 550℃. It has been found that the nucleation layer's surface roughness is a critical factor on the epitaxial layer's quality. When a nucleation layer is grown with an EDMIn flow rate of 2.3 μmole/min for 12 minutes, the surface roughness of the nucleation layer is minimum and the successively grown epitaxial layer's qualities are comparable to those of the homoepitaxial InP layers reported. The minimum full width at half maximum of InP (200) x-ray diffraction peak and that of near-band-edge peak from a 4.4 K photoluminescence are 60 arcmin and 6.33 meV, respectively.Keywords: InP, Heteroepitaxy, Surface roughness, Nucleation layer

TBP를 이용한 InP 에피층의 MOVPE 성장

TBP (tertiarybutylphosphine), a relatively new material for phosphorus, has been studied with EDMIn (ethyldimethylindium) as an indium source for the growth of InP by MOVPE (metalorganic vapor phase epitaxy). Mirror smooth and good crystalline InP layers were obtained at <TEX>$500-600^{\circ}C$</TEX> with the TBP/EDMIn molar ratio as low as 21. The deposited InP layers are all n-type with the electron concentration in the range of (5-10)<TEX>${\times}10^{16}\;cm^{-3}$</TEX>, which is a lot higher than those from <TEX>$PH_3$</TEX>. This high concentration is due presumably to the high concentration of donor impurities in TBP. And it has been found that the formation of adduct occurs between EDMIn and TBP at room temperature when the partial pressure of EDMIn in the reactant mixture is above <TEX>$1{\times}10^{-2}$</TEX> Torr. The high concentration of impurities in TBP and the adduct formation between EDMIn and TBP are major obstacles in replacing <TEX>$PH_3$</TEX> and TMIn for the growth of device quality InP layers.

Chemical beam epitaxial growth of GaInP using uncracked trisdimethylaminophosphine

Gallium indium phosphide (Ga x In1−x P) epitaxial layers were grown on GaAs substrates by chemical beam epitaxy (CBE) without thermally precracking the group V precursor. Trisdimethylaminophosphine (TDMAP), triisopropylgallium (TIPGa), and ethyldimethylindium (EDMIn) were used as the phosphorus, gallium and indium sources, respectively. Ga x In1−x P was grown without group V precracking for substrate temperatures in the range of 400–520 °C. Above 500 °C, the epilayers had a hazy appearance presumably due to being phosphorus deficit. A strong solid composition dependence on substrate temperature was observed. The samples were In-rich at low growth temperatures and Ga-rich at high growth temperatures. It was possible to grow the Ga x In1−x P epilayers over a large composition range with good morphology and strong photoluminescence. Values of full width at half maximum were as low as 45 meV at 14 K photoluminescence measurements.

GaAs 기판 위에 EDMIn과 TBP로부터 성장되고 양극산화 처리된 InP Schottky Diode

Au/oxide/n-InP Schottky diodes were fabricated from heteroepitaxial InP layers grown on GaAs substrates by the metalorganic vapor phase epitaxy (MOVPE) method from a new combination of source materials: ethyldimethylindium (EDMIn) and tertiarybutylphosphine (TBP). Anodic oxidation technique by using a solution of 10 g of ammonium pentaborate in 100 cc of ethylene glycole as the electrolyte was used to deposit a thin oxide layer. The barrier heights determined from three different techniques, current-voltage (I-V) measurements at room temperature and in the temperature range of 273 K - 373 K, and room temperature capacitance-voltage (C-V) measurements are in good agreement, 0.7 - 0.9 eV which is considerably high as compared to the 0.45 - 0.55 eV in Au/n-InP Schottky diode without a Passivation layer. The ideality factors of 1.1 - 1.3 of the Schottky diodes were also determined from the I-Y characteristics. Deep level transient spectroscopy (DLTS) studies revealed only one shallow electron state at 92.6 meV below the bottom of the conduction band and no deep state in the heteroepitaxial InP layers grown from EDMIn and TBP.

Chemical beam epitaxial growth of inp using EDMIn and BPE

The effect of the growth temperature on the quality of InP grown by chemical beam epitaxy (CBE) using ethyldimethylindium (EDMIn) and bisphos-phinoethane (BPE) are presented. The growth rate was nearly independent of growth temperature, BPE flow rate, and cracker cell temperature in the range from 700 to 900°C. Smooth and mirror-like surfaces were obtained for all of the samples grown at temperatures above 465°C. All of the InP samples were n-type. As the growth temperature increased, the net carrier concentration decreased and reached a minimum value of 3.2× 1015 cm−3 at 485°C. The electron mobility increased with increasing growth temperature, reaching values of 3630 and 21800 cm2/Vs at 300 and 77K, respectively. The photoluminescence was found to depend strongly on the growth temperature. Excitonic luminescence was detected only for growth temperatures above 465°C. The intensity of the band edge emission is comparable to that of the acceptor related emission for layers grown at 465°C. At 485°C, the band-edge recombination is dominant and the acceptor related emission is barely observable. As the growth temperature increased from 465 to 485°C, the full width at half maximum of the bound exciton peak decreased from 6.8 to 3.5 meV at 14K. This trend was consistent with the decrease in the impurity concentration deduced from the Hall effect measurements.

CBE growth of InP using BPE and TBP: a comparative study

Results of a comparative study on the growth of indium phosphide (InP) by chemical beam epitaxy (CBE) using two alternative phosphorous (P)-precursors, bisphosphinoethane (BPE) and tertiarybutylphosphine (TBP), are presented. For both P-precursors, ethyldimethylindium (EDMIn) was used as the indium (In) precursor. TBP has gained wide acceptance in gas phase growth techniques such as organometallic vapor phase epitaxy (OMVPE) and CBE and its variants. However, BPE has not been extensively applied to CBE growth with only preliminary results of CBE-grown InP using BPE having been published to date. This paper presents the first systematic study on the growth rate and efficiency, morphology, electrical and optical properties of CBE-grown InP using BPE. We compare these results to data obtained for CBE-grown InP using TBP. To make this comparison more meaningful, all TBP and BPE growth runs were performed in sequence using the same CBE hardware under identical experimental conditions. Duplicate sets of sample runs were grown to verify reproducibility. Details of the effects of substrate temperature, cracker cell temperature and V III ratio on the electrical transport properties determined from 77 K and room-temperature Hall measurements and the optical properties characterized by 14 K photoluminescence (PL) measurements are presented. The Hall carrier concentrations and PL data strongly correlate with the sulfur impurity levels measured by secondary ion mass spectroscopy (SIMS). All of the undoped InP epitaxial layers show n-type conductivity. Striking similarities in the electrical and optical properties of InP grown using either BPE or TBP were observed indicating that BPE and TBP, in many respects, can be viewed as interchangeable P-sources.

Selective epitaxial growth of GaInP by LP-MOCVD using ethyldimethylindium, trimethylindium, trimethylgallium and triethylgallium as group III sources

The present experiments demonstrate the epitaxial growth (EG) and selective epitaxial growth (SEG) of GaInP by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) using ethyldimethylindium (EDMI), trimethylindium (TMI), trimethylgallium (TMG) and triethylgallium (TEG) as group III sources. In epitaxial growth of GaInP, the Ga incorporation efficiency using TEG + EDMI is found to be lower than those using other combinations. Completely selective epitaxy using TEGa + EDMIn can be achieved at a growth temperature of 675°C and at a growth pressure of 40 Torr, while other combinations (TEG + TMI, TMG + TMI, and TMG + EDMI) can achieve SEG of GaInP at 650°C. High resolution double-crystal X-ray measurements are used to investigate the compositional variation in the selectively epitaxial-grown area.

Characterization of GaP / InGaP and GaP / GaAsP strained-layer quantum wells grown by metalorganic chemical vapor deposition

GaP/InGaP and GaP/GaAsP strained-layer quantum well (QW) structures with 3.0–5.0 nm thick well layers in the direct gap region were grown on GaP substrates by metalorganic chemical vapor deposition (MOCVD) using triethylgallium (TEGa) and ethyldimethylindium (EDMIn) for the column III sources and 100% AsH 3 and PH 3 for the column V sources. The strained QW structures were characterized using TEM and 4.2 K photoluminescence (PL). Transmission electron microscope (TEM) images indicate that the structures are uniform with sharp, defect-free interfaces. The QW layers are clearly resolved and appear to be free of misfit dislocations or other defects. The InGaP QW structures exhibit improved 4.2 K PL linewidths and a shift of the peak energies to shorter wavelengths compared to InGaP bulk layers of the same compositions. The GaAsP QW structures also exhibit sharp PL emission linewidths. The band alignments for the GaP/InGaP and GaP/GaAsP strained heterojunctions were calculated using local-density-functional pseudopotential formalism and the model-solid approach. Optical transition energies between the conduction band and valence subbands at the Γ point were calculated for the InGaP and GaAsP strained QWs, taking into account both the strain-modified band structures and quantum confinement effects. By employing the results derived from the theoretical predictions, we show that the 4.2 K PL spectra of the InGaP strained wells exhibit both the n = 1 heavy-hole and light-hole related transitions. We also show that the degree of removal of valence band degeneracy can be determined from the PL spectra.

Selective epitaxial growth of GaInP by low-pressure metal-organic chemical-vapor deposition using ethyldimethylindium as In source

We have demonstrated the feasibility of selective epitaxial growth (SEG) of GaInP using low-pressure metal-organic chemical-vapor deposition (LPMOCVD) with the combination of ethyldimethylindium (EDMIn) and triethylgallium (TEGa) as the group-III sources. Complete selective epitaxy can be achieved at a growth temperature of 675 °C and a growth pressure of 40 Torr. The deposition of Ga-rich polycrystalline GaInP on Si3N4 film occurs at lower temperatures. Although the incorporation efficiency of TEGa into GaInP is much lower than that of trimethylgallium, the combination of EDMIn and TEGa has been found to be a good candidate for SEG of GaInP. Low-temperature photoluminescence shows that the selectively grown epitaxial layer has good optical quality and is useful for light emitting device applications.

InAsBi alloys grown by organometallic vapor phase epitaxy

InAsBi is a III/V alloy with potential application for detectors in the 8–12 μm region of the spectrum. Growth of InAs 1- x Bi x , with x ≤ 0.054, at 350°C by atmospheric pressure organometallic vapor phase epitaxy has been made possible by using a new combination of precursors, ethyldimethylindium (EDMIn), tertiarybutylarsine (TBAs) and trimethylbismuth (TMBi). Results were obtained using a V/III ratio between 21 and 22. With these conditions, a Bi distribution coefficient of 1.746 was measured. X-ray diffraction verifies that Bi incorporates substitutionally into the zincblende structure. For x < 0.045, it was possible to suppress whisker formation and obtain excellent surface morphology. Measurement of photoluminescence for x ≤ 0.037 indicates good crystal quality. The measured rate of change of bandgap with Bi concentration, d E g/d x = -55 meV/%Bi, indicates that a 77 K bandgap energy of E = 0.10 eV should be reached with an alloy composition of InAs 0.94Bi 0.06.

Metalorganic vapor phase epitaxical growth and 1.5-μm laser fabrication using ethyldimethylindium, tertiarybutylphosphine, and tertiarybutylarsine

High-quality InGaAsP lattice matched to InP was grown by low-pressure metalorganic vapor phase epitaxy using ethyldimethylindium (EDMIn), tertiarybutylphosphine (TBP), and tertiarybutylarsine (TBA). The background carrier concentrations of undoped InP and InGaAs were as low as 1.5×1015 and 2.2×1015 cm−3, respectively. Good compositional control of In-GaAsP was also possible. The performance of the double heterostructure wafers employed as lasers as characterized by threshold current density, internal loss, and internal quantum efficiency. The threshold current density for a 300-μm cavity was as low as 2.0 kA/cm2. In addition, ridge-waveguide distributed feedback lasers were successfully fabricated. These results show that EDMIn, TBP, and TBA might be used to replace conventional sources for growing InGaAsP/InP lasers.

Characterization of InP grown by low-pressure MOVPE using ethyldimethylindium and tertiarybutylphosphine

A new source material combination of ethyldimethylindium (EDMIn) and tertiarybutylphosphine (TBP) is used for low-pressure metalorganic vapor phase epitaxy (MOVPE) of InP. The growth rate dependence on the V/III ratios indicates that a EDMIn:TBP parasitic reaction exists. However, InP layers grown using EDMIn and TBP show good electrical and optical properties, comparable to those using a conventional source material combination of trimethylindium (TMI) and phosphine (PH 3). The highest electron mobility at 77 K is 56,000 cm 2/V · s with a free carrier concentration of 1.0 × 10 15 cm -3. Sharp and well resolved exciton peaks were observed in 4.0 K PL spectra.

Growth and characterization of indium arsenide thin films

The growth and characterization of indium arsenide films grown on indium phosphide substrates by the metal organic chemical vapor deposition (MOCVD) process is reported. Either ethyl dimethyl indium or trimethyl indium were found to be suitable in combination with arsine as source compounds. The highest electron mobilities were observed in films nucleated at reduced growth temperature. Scanning electron microscopy studies show that film nucleation at low temperature prevents thermal etch pits from forming on the InP surface before growth proceeds at an elevated temperature. Electron mobilities as high as 21,000 cm2V−1 sec−1 at 300 K were thus obtained for a film only 3.4 μm thick. This mobility is significantly higher than was previously observed in InAs films grown by MOCVD. From the depth dependence of transport properties, we find that in our films electrons are accumulated near the air interface of the film, presumably by positive ions in the native oxide. The mobility is limited by electrons scattering predominantly from ionized impurities at low temperature and from lattice vibrations and dislocations at high temperature. However, scattering from dislocations is greatly reduced in the surface accumulation layer due to screening by a high density of electrons. These dislocations arise from lattice mismatch and interface disorder at the film-substrate interface, preventing these films from obtaining mobility values of bulk indium arsenide.

Temperature-dependent ultraviolet absorption spectra of group IIIb and Vb compounds used in photo-assisted chemical vapor deposition

The ultraviolet (UV) absorption cross sections from 185 to 320 nm have been measured for four group IIIb and two Vb alkyl compounds. These are trimethylaluminum (TMAl), trimethylgallium (TMGa), triethylgallium (TEGa), ethyldimethylindium (EDMIn), trimethylarsenic (TMAs), and tertiarybutylphosphine (TBP). In the case of ethyldimethylindium (EDMIn) and tertiarybutylphosphine (TBP), the UV absorption spectra have not been previously recorded. The UV absorption cross sections were measured at 193, 222, and 248 nm; wavelengths that are readily achieved with commercially available excimer lasers. The UV spectra of the group IIIb compounds show a weak long-wavelength absorption followed by a strong absorption, while those of the group Vb compounds show a sharp cutoff in the long-wavelength end of a strong absorption. TMGa, TEGa, and TMAs exhibit a decreasing absorption with increasing temperature. However, with an increase of temperature, the absorption of TMAl increases rapidly and the absorption extends towards longer wavelengths, reflecting dissociation of the dimer into monomer at higher temperatures. A simple molecular orbital model by Walsh is used to interpret the UV spectra of these metal alkyl compounds.

MOCVD growth of InGaAlP using ethyldimethylindium as an In source and application to visible-region lasers

Ethyldimethylindium (EDMI) has been investigated as a new metalorganic In source for the MOCVD growth of InGaAlP, and it was compared with trimethylindium (TMI). Good compositional control for InGaAlP was possible using EDMI. The indium incorporation efficiency from EDMI is higher than that from TMI. Undoped InGaP and InAlP layers grown using EDMI have a donor concentration ( N D) about 3 × 10 16 cm -3 higher than that those grown using TMI. High residual donor concentration in InGaAlP grown using EDMI affects the Zn doping characteristics. Si doping characteristics of InGaAlP grown from EDMI are almost the same as those when growth is from TMI. The inner stripe visible-region (670 nm) laser operation was achieved using DH wafers grown from EDMI. Excellent laser characteristics, such as a threshold current of 66 mA and a maximum cw operation temperature of 78°C, were obtained. These characteristics are comparable with those of lasers grown from TMI.

Heteroepitaxial Growth of ImP and GaInAs on GaAs Substrates Using Tertiarybutylarsine and Tertiarybutylphosphine

ABSTRACTThe heteroepitaxial growth of InP and GaInAs on GaAs substrates has been studied by using a new combination of source materials: ethyldimethylindium (EDMIn) and trimethylgallium (TMGa) or triethylgallium (TEGa) as group III sources, and tertiarybutylphosphine (TBP) and tertiarybutylarsine (TBAs) as group V sources. The heteroepitaxial growth was carried out in a horizontal reactor in H2 under atmospheric pressure using a 2 kW quartz lamp as the substrate heater. Epitaxial InP layers of good surface morphology were obtained by using a two step process. The continuity and thickness of the buffer layer are important parameters. The InP layers deposited at 600°C are n-type, and the electron concentration decreases with decreasing TBP/EDMIn molar ratio. The 4.2 K photoluminescence of InP films is very similar to that of homoepitaxial InP films deposited at 600°C using trimethylindium (TMIn) and phosphine. Epitaxial GaxIn1–xAs layers with In composition varying from 3% to 53% have been deposltedi on GaAs substrates at 500° -550°C. A single growth step can be used for the deposition of GaxIn1–xAs with In composition of less than 20%. An InP buffer layer was used when the GaxIn1–xAS layer contains about 53% In. The composition of GaInAs was determined by optical absorption and photoluminescence techniques.

Ethyldimethylindium for the growth of InGaAs-GaAs strained-layer lasers by metalorganic chemical vapor deposition

The growth and characterization of strained In0.25Ga0.75As-GaAs-Al0.20Ga0.80As quantum well lasers grown by metalorganic chemical vapor deposition using ethyldimethylindium (EDMIn) are described. A vapor pressure of 0.56 Torr at 11 °C has been extracted from the growth rates of thin InGaAs layers by transmission electron microscopy. Data on reproducibility in quantum well size are presented which indicate long-term stability in the EDMIn vapor pressure. Laser performance in samples grown with EDMIn is equivalent to, and in some cases better than, those grown with trimethylindium.

Comparison of ethyldimethylindium (EDMIn) and trimethylindium (TMIn) for GaInAs and InP growth by LP-MOVPE

Using TMIn and EDMIn we have carried out a direct comparison of growth behavior of both materials in the standard LP-MOVPE system by growing InP and GaInAs. At identical TMIn and EDMIn partial pressures, the growth rate of InP is nearly 100% higher by using the latter compound, indicating that the growth efficiency is increased due to a lower thermal stability of the EDMIn. High purity InP and GaInAs layers have been obtained for the first time from this material. InP layers grown on 2 inch substrates reproducibly show carrier concentrations around 1014 cm−3 and electron mobilities at 77 K of 109,000 cm2/V·s. GaInAs layer with homogeneous film composition could be grown on 2 inch InP substrates. X-ray rocking curves show a FWHM of less than 30 arc sec which equals 10−4 lattice constants. Carrier concentrations were in the low 1015 cm−3 range and electron mobilities around 9500 cm2/V·s at 300 K and 45,000 cm2/V·s at 77 K reproducibly.

OMVPE growth of InP and Ga0.47ln0.53as using ethyldimethylindium

We report the organometallic vapor phase epitaxial (OMVPE) growth of InP and Ga0.47In0.53As using a new organometallic indium source, ethyldimethylindium (EDMIn), rather than the traditional sources triethylindium (TEIn) or trimethylindium (TMIn). EDMIn is a liquid at room temperature and its vapor pressure at 17° C was found to be 0.85 Torr using thermal decomposition experiments. The growth results using EDMIn were compared to those using TMIn in the same atmospheric pressure reactor. For InP, use of EDMIn resulted in a high growth efficiency of 1.3 × 104 μm/ mole, which was independent of the growth temperature and comparable to the growth efficiency obtained with TMIn. The high growth efficiency is consistent with the observation of no visible parasitic gas phase reactions upstream of the substrate. The 4K photoluminescence (PL) spectra consist of a peak due to bound excitons and an impurity related peak 38 meV lower in energy. This impurity peak is ascribed to conduction band to acceptor transitions from carbon, due to the decreasing relative intensity of this peak with increasing V/III ratio. The relative intensity of the C impurity peak decreases by five times when the growth temperature is increased from 575 to 675° C, with a corresponding increase in the room temperature electron mobility from 725 to 3875 cm2/ Vs. For GalnAs lattice-matched to InP, use of EDMIn also resulted in a temperatureindependent high growth efficiency of 1.0 x 104 μm/mole, indicating negligible parasitic reactions with AsH3. The In distribution coefficient was nearly constant at a value of 0.9, however the run to run composition variation was slightly higher for EDMIn than for TMIn. The 4K PL showed donor-acceptor pair transitions due to C and Zn. The C impurity peak intensity decreased dramatically with increasing growth temperature, accompanied by an increase in the room temperature electron mobility to 5200 cm2/Vs. Overall, the growth of both InP and GalnAs using EDMIn was qualitatively similar to that using TMIn, although the room temperature electron mobilities were lower for the new source than for our highest purity bottle of TMIn.