High Speed Rotating Disk Reactor Research Articles

Growth of ZnO Thin Films by Using MOCVD with a High-Speed Rotating Disk Reactor

ZnO thin films were grown by using MOCVD with separated nozzles and a vertical-type highspeed rotating disk reactor. The interaction between source gases is prevented by the separated nozzles. The high-speed disk rotating system realized laminar flow by suppressing the thermallyinduced buoyancy flow, and it will be possible to inhibit the oxygen vacancies because the source gases are attracted on the substrate by the centripetal force. High thickness uniformity of below 2.0 % variation was obtained in 2-inch-diameter wafers. The results of the photoluminescence and the Hall-effect measurements were compared to the results obtained for conventional horizontal-type reactor and showed a suppression of the green emission band and of the carrier concentration, which shows the advantage of the high-speed rotating disk reactor.

High uniformity of InGaAsP layers grown by multi-wafer MOVPE system

Compositional uniformity of lattice-matched quaternary (InGaAsP) epitaxial layers on InP substrate was examined with multi-wafer MOVPE growth. Epitaxial layers with the photoluminescence (PL) wavelength of 1.3 μm were obtained with compositional uniformity standard deviation of 0.80 nm in all four wafers, and 0.97 nm in all six wafers for the same growth batch. The vertical high-speed rotating-disk reactor was used to grow the epitaxial layers on four or six 2″ InP wafers for the same growth batch. Compositional uniformity depends on wafer temperature that attributes to the thermal contact resistance between a wafer and a wafer carrier. It is important to suppress the temperature difference between them. The structure of the wafer carrier was optimized by computational fluid dynamics (CFD) analysis in order to compensate the thermal contact resistance. The wafer carrier temperature was successfully controlled to the same as the wafer, so that compositional uniformity of epitaxial layers was improved.

The growth and characterization of GaInAsSb and AlGaAsSb on GaSb by metal-organic chemical vapor deposition

The growth conditions for GaInAsSb and AlGaAsSb using metal-organic chemical vapor deposition in an high speed rotating disk reactor are described. Trimethylindium, triethylgallium, arsine, and trimethylantimony were used as precursors for the growth of GaInAsSb. Triethylgallium, ethyldimethylamine alane, triethylantimony, and arsine were the precursors used for the growth of AlGaAsSb. These materials were doped both n- and p-type using a mixture of diethyltellurium and diethylzinc as sources. An optimum growth temperature of 520°C was determined for the growth of GaInAsSb. Growth at this temperature yielded a root-mean-square (rms) surface roughness of 0.142nm. AlGaAsSb could be grown over the range of 500–600°C with somewhat rougher surfaces (rms>0.7nm). The photoluminescence was found to correlate with surface roughness, increasing with smoother surfaces. AlGaAsSb mesa isolated diodes were prepared and characterized. These diodes showed good current-voltage characteristics with breakdown voltages greater than −6V.

InAsSb/InPSb strained-layer superlattice growth using metal-organic chemical vapor deposition

We report on the metal-organic chemical vapor deposition (MOCVD) of strained layer superlattices (SLSs) of InAsSb/InPSb as well as mid-infrared optically pumped lasers grown using a high-speed rotating disk reactor (RDR). The devices contain AlAsSb cladding layers and strained, type-I, InAsSb/InPSb active regions. By changing the layer thickness and composition of InAsSb/InPSb SLSs, we have prepared structures with low-temperature (<20 K) photoluminescence wavelengths ranging from 3.4 to 4.8 μm. We find a variation in band gap of 0.272–0.324 eV for layer thicknesses of 9.0–18.2 nm. From these data we have estimated a valence band offset for the InAsSb/InPSb interface of about 400 meV. The optical properties of the superlattices revealed an anomalous low-energy transition that can be assigned to an antimony-rich interfacial layer in the superlattice. An InAsSb/InPSb SLS, laser was grown on an InAs substrate with AlAs 0.16Sb 0.84 cladding layers. A lasing threshold and spectrally narrowed laser emission were seen from 80–200 K, the maximum temperature where lasing occurred. The temperature dependence of the SLS laser threshold is described by a characteristic temperature, T 0=72 K, from 80 to 200 K.

Exploring new active regions for type I InAsSb strained-layer lasers

We report on the metal-organic chemical vapor deposition (MOCVD) of mid- infrared InAsSb/InPSb optically pumped lasers grown using a high speed rotating disk reactor (RDR). The devices contain AlAsSb claddings and strained, type 1, InAsSb/InPSb active regions. By changing the layer thickness and composition of InAsSb/InPSb SLSs, we have prepared structures with low temperature ( 0.l6 Sb 0.84 claddings. A lasing threshold and spectrally narrowed laser emission was seen from 80 K through 200 K, the maximum temperature where Iasing occurred. The temperature dependence of the SLS laser threshold is described by a characteristic temperature, T 0 = 72 K, from 80 to 200 K.

The Growth of InAsSb/InAs/InPSb/InAs Mid-Infrared Emitters by Metal-Organic Chemical Vapor Deposition

AbstractWe report on the metal-organic chemical vapor deposition (MOCVD) of strained layer superlattices (SLSs) of InAsSb/InAs/InPSb/InAs as well as mid-infrared optically pumped lasers grown using a high speed rotating disk reactor (RDR). The devices contain AlAsSb cladding layers and strained, type I, InAsSb/InAs/InPSb/InAs strained layer superlattice (SLS) active regions. By changing the layer thickness and composition of the SLS, we have prepared structures with low temperature (&lt;20K) photoluminescence wavelengths ranging from 3.4 to 4.8 µm. The optical properties of the InAsSb/InPSb superlattices revealed an anomalous low energy transition that can be assigned to an antimony-rich, interfacial layer in the superlattice. This low energy transition can be eliminated by introducing a 1.Onm InAs layer between the InAsSb and InPSb layers in the superlattice. An InAsSb/InAs/InPSb/InAs SLS laser was grown on an InAs substrate with AlAs0.16Sb0.844cladding layers. A lasing threshold and spectrally narrowed laser emission were seen from 80 through 250 K, the maximum temperature where lasing occurred. The temperature dependence of the SLS laser threshold is described by a characteristic temperature, T0 = 39 K, from 80 to 200 K.

Progress in the growth of mid-infrared InAsSb emitters by metal-organic chemical vapor deposition

We report on recent progress and improvements in the metal-organic chemical vapor deposition (MOCVD) of mid-infrared InAsSb emitters using a high speed rotating disk reactor (RDR). The devices contain AlAsSb claddings and strained InAsSb active regions. These emitters have multi-stage, type I, InAsSb/InAsP quantum well active regions. A semi-metal GaAsSb/InAs layer acts as an internal electron source for the multi-stage injection lasers and AlAsSb is the electron confinement layer. These structures are the first MOCVD multi-stage devices. Growth in an RDR was necessary to avoid the previously observed Al memory effects found in a horizontal reactor. Broadband LEDs produced 2 mW average power at 3.7 μm and 80 K and 0.1 mW at 4.3 μm and 300 K. A multi-stage, 3.8–3.9 μm laser structure operated up to T=180 K. At 80 K, peak-power >100 mW/facet and a high slope-efficiency (48%) were observed in these gain guided lasers.

The growth of AlInSb by metalorganic chemical vapor deposition

We have grown AlxIn1−xSb epitaxial layers by metalorganic chemical vapor deposition using tritertiarybutylaluminum (TTBAl), trimethylindium (TMIn), and triethylantimony (TESb) as sources in a high speed rotating disk reactor. Growth temperatures of 435 to 505°C at 200 Torr were investigated. The V/III ratio was varied from 1.6 to 7.2 and TTBAl/(TTBAl+TMIn) ratios of 0.26 to 0.82 were investigated. AlxIn1−xSb compositions from x=0.002 to 0.52 were grown with TTBAl/(TTBAl+TMIn) ratios of 0.62 to 0.82. Under these conditions, no Al was incorporated for TTBAl/(TTBAl+TMIn) ratios less than 0.62. Hall measurements of AlxIn1−xSb showed hole concentrations between 5×1016 cm−3 to 2 × 1017 cm−3 and mobilities of 24 to 91 cm2/Vs for not intentionally doped AlxIn1−xSb.

Transparent and conductive Ga-doped ZnO films grown by low pressure metal organic chemical vapor deposition

Highly transparent conductive Ga-doped zinc oxide (ZnO:Ga) has been deposited on 3 in.×4 in. Corning 7059 glass and other substrates using a high speed rotating disk reactor low pressure metal organic chemical vapor deposition system. Diethylzinc, oxygen, and triethylgallium were used as precursors. The films exhibit low resistivity, ∼2.6×10−4 Ω cm, high optical transparency (&amp;gt;85%) in the visible range, good adhesion, and are highly stable. The film properties were correlated with the growth conditions, including flow rate, temperature, pressure, and doping concentrations. The microstructural properties of the films, such as surface and interface morphology, crystallinity, and composition were studied using scanning electron microscopy, x-ray diffraction, and secondary ion mass spectroscopy. The resistivity and transmittance of the films were investigated by four-point probe measurements, photoluminescence spectroscopy, and optical absorption spectroscopy. In order to meet the needs for application to flat panel displays, the thermal stability of the Ga-doped ZnO films have been tested by a dc biased heater. The feasibility of film processing was also investigated through patterning and wet chemical etching.

Recent Progress in the Growth of Mid-ir Emitters by Metalorganic Chemical Vapor Deposition

AbstractWe report on recent progress and improvements in the metal-organic chemical vapor deposition (MOCVD) growth of mid-infrared lasers and using a high speed rotating disk reactor (RDR). The devices contain AlAsSb claddings and strained InAsSb active regions. These lasers have multi-stage, type I InAsSb/InAsP quantum well active regions. A semi-metal GaAsSb/InAs layer acts as an internal electron source for the multi-stage injection lasers and AlAsSb is an electron confinement layer. These structures are the first MOCVD multi-stage devices. Growth in an RDR was necessary to avoid the previously observed Al memory effects found in conventional horizontal reactors. A single stage, optically pumped laser yielded improved power (&gt; 650 mW/facet) at 80 K and 3.8 μm. A multi-stage 3.8–3.9 μm laser structure operated up to T=170 K. At 80 K, peak power &gt; 100 mW and a high slope-efficiency were observed in gain guided lasers.

The Growth of InGaN/(Al)GaN Quantum Well Structures in a Multi-Wafer High Speed Rotating Disk Reactor

In the past year, several organizations have fabricated reliable, high-brightness LEDs from III-Nitride materials that emit in the blue and green. Recently, Nichia in Japan have announced lasing action in GaN-based diodes. Quantum well structures are key to all these results, offering higher brightness, narrower EL linewidths, and a wider spectral range. In order for the III-Nitride technology to develop, the material growth technique must offer high volume at low cost in addition to the requisite device performance. To date, only MOVPE has demonstrated this capability. We have previously reported the growth of GaN, InGaN, and AlGaN layers by MOVPE in a multi-wafer, high-speed rotating disk reactor. Both n- and p-doping and high quality optical properties have been achieved. In this paper we extend this earlier work and present results of the performance of InGaN / (Al)GaN quantum well structures. Intense PL spectra were observed in the violet and blue regions. The thinnest wells show evidence from PL and DCXRD measurments of either discontinuous layers (islands) or a diffuse upper interface, with preliminary TEM results showing the latter to be the most likely. We also report excellent uniformity of these quantum well structures, and show electroluminescence from a SQW diode emitting at 473 nm.

Metalorganic chemical vapor deposition growth of high-quality and highly uniform strained InGaAs quantum wells in a high-speed rotating-disk reactor

High-quality and highly uniform strained InGaAs/ AlGaAs quantum-well structures have been grown successfully metalorganic chemical vapor deposition (MOCVD) using a high-speed rotating-disk reactor in which growth on three wafers of 3-inch diameter can be carried out simultaneously. By rotating the susceptor disk at a speed as high as 1000 rpm, the excellent uniformity of the quantum-well structure has been obtained. It is ascertained that the controllability of the InAs composition in InGaAs layers is high enough at a growth temperature of 675°C, which is almost the same as the optimum growth temperature for AlGaAs layers. As a result, InGaAs/ AlGaAs quantum-well lasers emitting at 980 nm have been obtained without changing the growth temperature. The fabricated lasers exhibit an excellent uniformity of the lasing wavelength (±0.09%) and a high output power (448 mW).

Mechanical, Thermal and Flow Dynamics Issues in Compound Semiconductor MOCVD Reactor Design

ABSTRACTIn recent years Metalorganic Chemical Vapor Deposition (MOCVD) becomes a key epitaxial process for a variety of compound semiconductor devices such as: GaAs/AlGaAs lasers, HEMTs, LEDs, photocathodes, solar cells, and MESFETs; InP/InGaAsP long wavelength lasers and detectors; InP/InGaAs quantum wells and detectors, etc. Development of reliable, high throughput equipment is a major task in the implementation of MOCVD into cost-effective manufacturings. We have used Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) software to model thermal, structural, and flow processes for the scaling of EMCORE vertical, high speed rotating disk reactor (RDR) to large dimensions (four 4″ wafers located on 12″ wafer carrier). Flow modeling was used to determine basic reactor geometry and the relation between process parameters such as total reactant flow, temperature, pressure, and rotation speed. Thermal and structural analysis was used to produce a uniform substrate temperature, avoid reactor overheating and decrease thermal stress. Flow and temperature distribution predicted by the modeling were found to be well correlated with experimental results.

MOCVD grown CdZn Te/GaAs/Si substrates for large-area HgCdTe IRFPAs

Large-area HgCdTe 480×640 thermal-expansion-matched hybrid focal plane arrays were achieved by substituting metalorganic chemical vapor deposition (MOCVD)-grown CdZnTe/GaAs/Si alternative substrate in place of bulk CdZnTe substrates for the growth of HgCdTe p-on-n double-layer heterojunctions by controllably-doped mercury-melt liquid phase epitaxy (LPE). (100) CdZnTe was grown by MOCVD on GaAs/Si using a vertical-flow high-speed rotating disk reactor which incorporates up to three two-inch diameter substrates. Layers having specular surface morphology, good crystalline structure, and surface macro defect densities <50 cm−2 are routinely achieved and both the composition uniformity and run-to-run reproducibility were very good. As the composition of the CdZnTe layers increases, the x-ray full width at half maximum (FWHM) increases; this is a characteristic of CdZnTe grown by VPE techniques and is apparently associated with phase separation. Despite a broader x-ray FWHM for the fernary CdZnTe, the FWHM of HgCdTe grown by LPE on these substrates decreases, particularly for [ZnTe] compositions near the lattice matching condition to HgCdTe. An additional benefit of the ternary CdZnTe is an improved surface morphology of the HgCdTe layers. Using these silicon-based substrates, we have demonstrated 78K high-performance LWIR HgCdTe 480×640 arrays and find that their performance is comparable to similar arrays fabricated on bulk CdZnTe substrates for temperatures exceeding approximately 78K. The performance at lower temperatures is apparently limited by the dislocation density which is typically in the low-mid 106 cm−2 range for these heteroepitaxial materials.

Uniform growth of InSb on GaAs in a rotating disk reactor by LP-MOVPE

Uniform films of InSb on GaAs substrates have been grown in a vertical, high-speed rotating disk reactor by low pressure MOVPE. Highly uniform and specular films were obtained over a 50 mm diameter wafer placed at the center of a 5 inch diameter wafer platter. Characterization of thickness, sheet resistance, mobility, and surface morphology was performed by SEM, sheet resistance mapping, Hall effect measurements, and Nomarski microscopy. Thickness uniformity, measured at 10 points radially across the wafer with a 3 mm edge exclusion, is as low as 1.84% with an average uniformity over several runs of only 2.8%. Results obtained from Hall mobility measurements taken by a 7 point cross-pattern show an average mobility of 41,030 cm 2/V · s with a coefficient of variation of 7.1% at 300 K. The sheet resistance uniformity, as determined by a 55 point, contactless, eddy current technique, shows a coefficient of variation as low as 1.37% with an average uniformity over 22 consecutive growth runs of only 3.1%. The effects of growth temperature and V/III ratio on the surface morphology and electronic properties were also studied, resulting in high quality epitaxial layers. With a growth temperature of 475°C and a V/III ratio of 18, Hall mobilities as high as 45,000 cm 2/V · s at 300 K and 31,500 cm 2/V · s at 77 K were measured on a 2 μm thick InSb layer. The corresponding carrier concentrations were 2.05×10 16 and 4.57×10 15 cm −3.

Metalorganic chemical vapor deposition of superconducting YBa2Cu3O7−x in a high-speed rotating disk reactor

Metalorganic chemical vapor deposition (MOCVD) of YBa2Cu3O7−x films on (100) SrTiO3 was performed in a high-speed rotating disk reactor. Metal β-diketonates were used as source materials. Energy dispersive spectroscopy analysis showed as-grown and post-annealed samples to have a composition matching that of superconducting thin-film standards. X-ray data showed the annealed films to be highly oriented with the c axis perpendicular to the substrate. The best films exhibited an onset temperature of 90 K and zero resistance at 88 K. The width of the superconductive transition (&amp;lt;2 K) is the best value thus far reported for 123 films grown in a commercially available MOCVD system.

Growth of InGaAsP films in a Multi-Wafer high Speed Rotating Disk Reactor by Mocvd

AbstractAs the demands for InP epitaxial materials grow, the need for larger throughput growth techniques becomes important. However, uniformity of thickness and particularly composition of InGaAs and InGaAsP films has proved troublesome. This has limited much of the InGaAsP growth work to single wafer machines. The purpose of this work is to demonstrate good film properties and uniformity on a multi-wafer machine that holds three, two-inch diameter wafers.