Pressure Organometallic Vapor Phase Epitaxy Research Articles

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.

Carbon doping of Ga xIn 1-xAs by atmospheric pressure organometallic vapour phase epitaxy

We have investigated the use of CCl 4 as a potential p-type dopant for Ga x In 1- x As by atmospheric pressure organometallic vapour phase epitaxy (AP-OMVPE), principally for applications lattice matched to InP. In contrast to results obtained by low pressure OMVPE, all layers grown on InP substrates were n-type; only layers with an alloy composition of x > 0.9 grown on GaAs substrates were p-type. Parasitic reactions involving Cl containing species complicated control of the alloy composition and attacked InP substrates, liberating P atoms which were found to be incorporated in some layers. In all cases the surface morphology was poor and we conclude that CCl 4 is not a useful dopant for Ga x In 1- x As under these conditions.

Selective regrowth of III–V epitaxial layers by low pressure organometallic vapor phase epitaxy using CCl4

The use of carbon tetrachloride was examined as a means of suppressing deposition on the dielectric mask during the selective regrowth of III–V epitaxial layers by organometallic vapor phase epitaxy. Highly anisotropic dry etching was used to form narrow (∼1 μm wide) trenches and mesas. Reentrant mesas were formed by wet chemical etching. Under conventional growth conditions, polycrystalline GaAs was deposited over the mask adjacent to the trenches. By adding CCl4, selectivity could be greatly enhanced; however the growth rate in the trenches was significantly increased due to lateral diffusion of the reactants upon desorption from the mask thereby making acceptable control of the growth rate difficult. Addition of CCl4 during the growth of InP and AlGaAs significantly improved the selectivity in the case of growth around etched mesas.

Low pressure OMVPE of ZnSe with hydrogen selenide and dimethylzinc-triethylamine

The growth and nitrogen doping of ZnSe by low pressure organometallic vapor phase epitaxy (OMVPE) have been investigated in a vertical downflow reactor equipped with a laser interferometer for in-situ growth rate measurements, and a microwave plasma cavity for precracking of ammonia for nitrogen doping. Particular emphasis is placed on understanding growth characteristics obtained with H2Se and the new adduct source dimethylzincrtriethylamine (DMZn:NEt3), as compared to those obtained with H2Se and DMZn. At higher temperatures and pressures, growth results obtained with DMZn:NEt3 are similar to those obtained using DMZn with the morphology exhibiting familiar hillock-shaped features. At lower temperatures (<300°C) and pressures (<30 Torr), growth rates are higher with the adduct source and the surface morphology is improved relative to films synthesized with DMZn. Hall measurements and photo-luminescence spectra of the grown films demonstrate that DMZn and DMZn:NEt3 produce material with comparable electronic and optical properties. Microwave plasma decomposition of ammonia is investigated as a possible approach to increasing nitrogen incorporation in ZnSe and photoluminescence spectra are compared to those realized with conventional ammonia doping.

Gas phase reactions of trimethylamine alane in low pressure organometallic vapor phase epitaxy of AlGaAs

We have investigated the effects of gas phase reactions between trimethylamine alane (TMAA), triethylgallium (TEG), and arsine on AlxGa1−xAs films grown by low pressure organometallic vapor phase epitaxy. The reactor used in this study provides for independent observation of the effects of TEG-TMAA and TMAA-arsine gas phase reactions. Gas phase reactions involving TMAA and TEG result in the formation of nonvolatile compounds upstream, which condense on the reactor wall, resulting in a reduction of growth rate and a degradation of the deposition uniformity. The TMAA-arsine reaction produces a compositional dependence on the gas phase stoichiometry (V/III ratio). Both of these effects are more severe for higher TMAA fluxes. High quality AlGaAs with excellent thickness and compositional uniformity was produced by spatially separating the TMAA and TEG in the gas phase which minimizes the parasitic reactions.

Band-gap narrowing in ordered Ga0.47In0.53As

We report the first observation of band-gap energy reduction in Ga0.47In0.53As deposited on (100) InP by atmospheric pressure organometallic vapor phase epitaxy due to CuPt-type ordering. A reduction of more than 65 meV in the band-gap energy is observed for lattice-matched samples that show strong CuPt-like ordering by transmission electron microscopy. By comparison samples that show no CuPt-like ordering diffraction signatures, do not have reduced band-gap energies. Studies of the influence of growth parameters on the band-gap energy indicate a U-shaped dependence on the growth temperature with a minimum around 550 °C and decreasing band-gap energies with increasing growth rate (at a constant V/III ratio) over the range 0.5–4 μm/h.

Strong photoluminescence from AlP/GaP disordered superlattice grown by atmospheric pressure organometallic vapor phase epitaxy using tertiarybutylphosphine

AlP/GaP disordered superlattices (d-SLs) are grown for the first time by atmospheric pressure organometallic vapor phase epitaxy using tertiarybutylphosphine as the phosphorous source. Strong photoluminescence (PL) is observed from the d-SL, comparing with the ordered superlattice (o-SL) and the bulk alloy (b-AL). The PL intensity of the d-SL is 158 times stronger than that of the o-SL and 114 times than that of the b-AL. The strong PL from the d-SL is attributed to the localized states created by the artificial disordering.

Epitaxial growth of AlGaInP lattice-matched to GaAsP substrates by organometallic vapor phase epitaxy

Ga 0.7In 0.3P is grown on GaAs 0.62P 0.38 substrates by atmospheric pressure organometallic vapor phase epitaxy and characterized with photoluminescence spectroscopy, double-crystal X-ray diffraction and transmission electron microscopy. The layers are free form defects when examined by transmission electron microscopy. They show bright orange, yellow and yellow green photoluminescence depending on composition. High quality (Al 0.7Ga 0.3) 0.7In 0.3P closely lattice-matched to the GaAsP substrate is also grown and doped with Si and Zn.

Low threshold Ga xIn 1− xP/(Al yGa 1− y) 0.5In 0.5P strained quantum well lasers

Strained Ga x In 1- x P/(Al y Ga 1- y ) 0.5In 0.5P quantum well (QW) lasers have been prepared by low pressure organometallic vapor phase epitaxy. By adjusting the QW active region composition and thickness, (300 K pulsed) wavelengths of 617 to 712 nm have been obtained. In the longer wavelength (λ > 670 nm) regime, where compressive strain ( x < 0.5) is applied, low threshold current density ( J th = 220 A/cm 2) and high characteristic temperature ( T 0 > 150 K) are demonstrated. For shorter wavelengths, where electron confinement begins to diminish, thresholds are higher and T 0 is lower, for both compressive- and tensile-strained ( x > 0.5) QWs. At 633 nm, best properties are J th = 400 A/cm 2 and T 0 = 60 K. The characteristic temperature can be improved by using multiple, rather than single, QWs.

Properties and use of cycled grown OMVPE GaAs:Zn, GaAs:Se, and GaAs:Si layers for high-conductance GaAs tunnel junctions

Heavily doped GaAs layers for high conductance GaAs tunnel junctions have been grown by atmospheric pressure organometallic vapor phase epitaxy (OMVPE) using Zn as the dopant for thep + regions and either Se or Si as the dopant for then + regions. At a growth temperature of 700° C using a “cycled” growth technique for the Zn-dopedp ++-GaAs layer, both the conductance and the peak current density of the tunnel diode has been increased by a factor of ∼65 compared to a tunnel junction with a continuously grown Zn-doped p+-GaAs. The conductance of the tunnel junction, which is maximized at a growth temperature of 650° C using cycled growth, is comparable to the best reported values for tunnel junctions grown by molecular beam epitaxy. Cycled growths forn + Se-doped regions are found to reduce the conductance of a tunnel junction by more than two orders of magnitude. However, cycled growth for the n+-GaAs regions with Si doping show no conductance degradation. A model based on incorporation sites of these dopants during OMVPE growth of GaAs is presented to account for the experimental observations.

Morphology of AlGaAs layer grown on GaAs(111)A substrate plane by organometallic vapor phase epitaxy

Growth behavior of AlGaAs heteroepitaxial layers on GaAs (111)A planes has been studied for atmospheric pressure organometallic vapor phase epitaxy. The Al composition as well as the arsine partial pressure and the growth temperature are the influential factors for the surface morphology of epitaxial layers on (111)A planes. By increasing the Al composition of grown layers, the range of growth conditions for obtaining a smooth surface morphology does not change so much. But the range for controlling defect structures, such as pyramidal shape, shifts to lower arsine partial pressures, and/or higher growth temperatures. The Al0.3Ga0.7As growth rate remains constant even at a lower arsine partial pressure than for the GaAs growth. This indicates that the morphology change is due to the increase in the arsine dissociation efficiency when the trimethylaluminum partial pressure increases.

Comparison of gallium and arsenic precursors for GaAs carbon doping by organometallic vapor phase epitaxy using CCl4

The carbon doping properties of GaAs grown by low pressure (30 Torr) organometallic vapor phase epitaxy at 520–700 °C with CCl4 as the dopant precursor were compared for the four possible combinations of trimethylgallium (TMGa), triethylgallium (TEGa), arsine (AsH3), and tertiarybutylarsine (TBAs). Secondary ion mass spectrometry (SIMS), Hall measurements, and infrared absorption were used to characterize the GaAs:C layers. Very high C-doping concentrations (∼1020 cm−3) could be obtained using either TMGa or TEGa and AsH3. The use of TBAs instead of AsH3 led to a significant reduction in carbon incorporation, by approximately a factor of 5–10 per mole of As precursor over the growth temperature range examined. Hydrogen at significant concentrations (1–6×1019 cm−3) was detected by SIMS in GaAs: C layers grown at ≤550 °C utilizing all four combinations of Ga/As precursors. The existence of electrically inactive C-H complexes was confirmed by observation of the C-H stretching mode at 2635 cm−1. A post-growth anneal under helium at 550 °C for 60 s removed the C-H pairs resulting in a 50%–100% increase in hole concentration. There was no change in the hole concentration for GaAs:C grown at ≥600 °C, indicating negligible hydrogen passivation.

Ultra-low temperature OMVPE of InAs and InAsBi

InAs and InAsBi have been grown by atmospheric pressure organometallic vapor phase epitaxy (OMVPE) over a broad temperature range from 600 to as low as 275° C. This is the lowest growth temperature ever reported for conventional OMVPE. It is demonstrated that lowering the growth temperature is the most effective approach for increasing the maximum Bi content in InAsBi alloys where the Bi solubility limit is 0.025 at.%. For example, InAsBi samples with Bi concentrations as high as 6.1 at.% have been successfully grown at a temperature of 275° C. Trimethylindium, arsine, and trimethylbismuth were used as precursors for most experiments. The growth efficiency is a constant for temperatures above 400° C, indicating that the growth rate is diffusion limited. For lower temperatures, it decreases exponentially with decreasing temperature with an activation energy of 24 kcal/mol. Incomplete pyrolysis of TMIn limits the growth rate in this temperature regime. By substituting ethyldimethylindium for TMIn the growth rate can be increased at lower temperatures. Hall effect measurements show that then-type background concentration increases from approximately 2.3 × 1016 to 1019 cm−3 as the growth temperature decreases from 600 to 325° C. Secondary ion mass spectroscopy results show that the dominant impurity is carbon. Thus, carbon is mainly a donor in these materials. The integrated photoluminescence intensity drops rapidly with decreasing growth temperature.

Low-threshold InGaAs strained-layer quantum-well lasers (λ=0.98 μm) with GaInP cladding layers and mass-transported buried heterostructure

Buried-heterostructure quantum-well lasers fabricated by mass transport are reported for In0.18Ga0.82As/GaAs/Ga0.5In0.5P strained-layer structures grown by atmospheric pressure organometallic vapor-phase epitaxy. Threshold current densities as low as 85 A/cm2 are measured for broad-stripe lasers, and buried-stripe devices show threshold currents as low as 3 mA and differential quantum efficiencies as high as 34% per facet without coatings.

Pyrolysis Studies and Deposition of Sb Films Using the Novel Omvpe Source (I-Pr)2 SbH

ABSTRACTThe novel antimony source compound di-isopropylantimony hydride, (i-Pr)2 was synthesized and evaluated for use as a volatile Sb-source compound for low temperature growth of Sb-containing semiconductor materials. (i-Pr)2SbH was pyrolyzed in a horizontal atmospheric pressure organometallic vapor phase epitaxy (OMVPE) reactor using Arand H2 as carrier gases. The gaseous exhaust products were analyzed by a residual gas analyzer. Complete pyrolysis of (i-Pr)2SbH in our OMVPE reactor occursaround 300°C and 350°C in Ar and H2, respectively. A comparison between the pyrolysis temperatures and pyrolysis byproducts with respect to a proposed decomposition mechanism of (i-Pr)2SbH is presented. Sb films were grown on Si(100) andSi(111) as low as 200° C. The Sb films were analyzed by Auger and X-ray diffraction. These polycrystalline Sb films were free of detectable carbon by AES. X-ray diffraction data indicated that these Sb films were highly oriented in the [000L] direction.

In-Situ Spectroscopic Ellipsometry Applied to ZnSe and ZnCdSe Growth Process in Organometallic Vapor Phase Epitaxy

ABSTRACTSpectroscopie ellipsometry is a well developed technique for studying the semiconductor materials and heterostructures. Here, we have applied this technique to in-situ studies of ZnSe and ZnCdSe growth in a low pressure organometallic vapor phase epitaxy system. The growth of ZnSe on GaAs was studied using a light source in the range 2 to 4 eV, and film thickness of a few tens of angstroms could be monitored by this technique. The band gap and the composition of Zn1-χCdχSe could also be measured as a function of real time. It was found that, for a gas phase DMCd composition of 60%, the amount of Cd incorporated in the layers is less than 25%. Spectroscopie ellipsometry is demonstrated to be a valuable technique for in-situ monitoring of semiconductor growth in organometallic vapor phase epitaxy systems.

Selective OMVPE of GaInAs and InP using a polycrystalline InP mask

InP and GaInAs were deposited on InP, by low pressure organometallic vapor phase epitaxy, in stripes opened in a layer of polycrystalline InP. Using polycrystalline InP as a mask eliminates growth spikes at the edge of the mask, and there is little (for GaInAs) or no (for InP) growth rate enhancement compared to growth on unmasked substrates. There is, however, a strong shift in the composition of GaInAs, the In mole fraction being much lower than for unmasked substrates. We explain this phenomenon by studying the difference of incorporation of In and Ga on substrates of different crystallographic orientations.

Investigation of organometallic vapor phase epitaxy of InAs and InAsBi at temperatures as low as 275 °C

InAs and InAsBi have been grown by atmospheric pressure organometallic vapor phase epitaxy (OMVPE) over a broad temperature range from 600 to as low as 275 °C. This is the lowest growth temperature ever reported for standard OMVPE. It is demonstrated that lowering the growth temperature is the most effective approach for increasing the Bi content in InAsBi alloys. For example, InAsBi samples with Bi concentrations as high as 6.1 at.% have been successfully grown at a temperature of 275 °C. Trimethylindium, arsine, and trimethylbismuth were used as precursors for most experiments. The growth efficiency is a constant for temperatures above 400 °C, indicating the growth rate is diffusion limited in this temperature regime. For lower temperatures, it decreases exponentially with decreasing temperature with an activation energy of 24 kcal/mol. Incomplete pyrolysis of TMIn limits the growth rate in this temperature regime. However, by substituting ethyldimethylindium for TMIn the diffusion controlled regime can be extended to lower temperatures. Hall effect measurements show that the n-type background concentration increases from approximately 2.3×1016 to 1019 cm−3 as the growth temperature decreases from 600 to 325 °C. Secondary-ion mass spectroscopy results show that the dominant impurity is carbon. Thus, carbon is mainly a donor in these materials.

High electron mobility in modulation-doped n-AlInAs/InP heterostructures grown by low pressure organometallic vapor phase epitaxy

We report high electron mobility in modulation-doped n-AlInAs/InP heterostructures. The electron mobility in these heterostructures was observed to be 48 500 cm2/V s with electron concentration of 8.1×1011/cm2 at 50 K. Shubnikov–de Hass measurement clearly shows the existence of two dimensional electron gas in this heterostructure. We also observed small light sensitivity and no persistent photoconductivity in this heterostructure, both of which are due to an AlInAs layer which is free of DX centers in an AlInAs and high quality heterointerface grown by low pressure organometallic vapor phase epitaxy.

Effect of growth temperature on photoluminescence of InAs grown by organometallic vapor phase epitaxy

Infrared photoluminescence (PL) from InAs epitaxial layers grown by atmospheric pressure organometallic vapor phase epitaxy (OMVPE) has been studied as a function of the growth temperature (350–600 °C). It is shown that the PL spectra depend strongly on the growth temperature. The integrated PL intensity decreases by about two orders of magnitude as the growth temperature decreases from 500 to 350 °C. In addition, Hall-effect measurements show that the n-type impurity concentration in InAs increases rapidly as the growth temperature decreases. The results of secondary-ion mass spectroscopy show that the dominant impurity is carbon and its concentration varies with the growth temperature in a similar way to the electron concentration. This confirms that carbon is a donor in InAs. The decreasing PL intensity with decreasing growth temperature is attributed to the increasing carbon concentration.