Organic Vapor Phase Deposition Research Articles

Organic Vapor Phase Deposition

Organic vapor phase deposition (OVPD) opens new opportunities in the control of composition and structure of organic thin films. The use of this recently developed process is examined for the growth of four archetypal organic systems: a crystalline organic salt (the optically nonlinear charge transfer salt DAST, see Figure), amorphous and polymeric organic films, and an optically pumped organic laser (Alq3 doped with Rhodamine 6G).

Depth-resolved cathodoluminescence study of ZnxCd1−xSe epilayer grown on (001) InP by metal organic chemical vapor phase deposition

Optical properties of zincblende structured ZnxCd1−xSe epilayer grown on InP by metal organic chemical vapor phase deposition at temperatures of 360, 400, and 440 °C are investigated with low temperature cathodoluminescence spectroscopy (CL). Both near band gap and deep level emissions are found for the samples grown at 400 °C and above, but deep level emissions are absent for the sample grown at 360 °C. We conclude that the growth temperature should be kept below the temperature at which InP begins to decompose and diffusion of III–V constituents into the epilayer occurs. Evidence of this diffusion comes from an analysis of depth resolved CL studies, which shows that the deep level emissions occur mainly at the epilayer/substrate interface. By monitoring the ratio of the intensity of the deep level emissions to that of the near band emissions, we find that this ratio is larger for samples grown at high temperatures than those at low temperatures. Indium diffusion from the substrate into the epilayer is most likely the source of these deep levels.

The properties of ZnSc layers grown on GaAs and Si substrates by atomic layer epitaxy

ZnSe layers have been grown by atomic layer epitaxy using metal organic vapor-phase deposition system on to (100) GaAs and (100) Si substrates. The growth rate per cycle is strongly dependent on the substrate temperature. The self-limiting growth of one monolayer per cycle is obtained in the wide substrate temperature range of 100–200°C for GaAs substrates and 150–250°C for Si substrates. The X-ray patterns are similar on both substrates. The surface morphologies are smooth and mirror-like. The photoluminescence spectra show an emission at 443 nm at 77 K on both substates.

Low pressure organic vapor phase deposition of small molecular weight organic light emitting device structures

A new technique for the deposition of amorphous organic thin films, low pressure organic vapor phase deposition (LP-OVPD), was used to fabricate organic light emitting devices (OLEDs) consisting of a film of aluminum tris-(8 hydroxyquinoline) (Alq3) grown on the surface of a film of N′-diphenyl-N,N′-bis(3-methylphenyl)1-1′biphenyl-4-4′diamine. The resulting heterojunction OLED was found to have a performance similar to conventional, small molecular weight OLEDs grown using thermal evaporation in vacuum. The LP-OVPD grown device has an external quantum efficiency of 0.40±0.05% and a turn-on voltage of approximately 6 V. The rapid throughput demonstrated with LP-OVPD has the potential to facilitate low cost mass production of conventional small molecule based OLEDs, and its use of low vacuum in a horizontal reactor lends itself to roll-to-roll deposition of organic films for many photonic device applications.

Low Pressure Organic Vapor Phase Deposition of Small Molecular Weight Organic Device Structures

AbstractA new technique for the deposition of amorphous organic thin films, low pressure organic vapor phase deposition (LP-OVPD), was used to fabricate organic light emitting devices (OLEDs) and optically pumped organic lasers. The OLED consisted of a film of aluminum tris- (8 hydroxyquinoline) (Alq3) grown on the surface of a film of N'-diphenyl-N,N'-bis(3- methylphenyl)1–l'biphenyl-4–4'diamine (TPD). Growth on both glass and polyester substrates was accomplished and the resulting heterojunction devices were found to have a performance similar to conventional, small molecular weight OLEDs grown using thermal evaporation in vacuum. The LP-OVPD grown OLED has an external quantum efficiency of 0.40 ± 0.05% and a turn-on voltage of approximately 6V. The optically pumped organic laser consisted of a film of Alq3 doped with the laser dye, benzoic acid, 2-[6-(ethylamino)-3-(ethylimino)-2,7-dimethyl-3Hxanthen- 9-yl]-ethyl ester, monohydrochloride (Rhodamine 6G). The laser output was centered at approximately 610nm and the lasing threshold was 30μJcm−2. The rapid throughput of LP-OVPD and its use of low vacuum in a horizontal reactor demonstrate its potential to facilitate low cost, roll-to-roll deposition of organic films for many photonic device applications.

Intense second harmonic generation and long-range structural ordering in thin films of an organic salt grown by organic vapor phase deposition

We discuss the growth of thin films of the organic salt, 4′-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) by the novel process of organic vapor phase deposition (OVPD). These films show long-range structural ordering and very intense second harmonic generation efficiencies (SHG) significantly greater (when normalized for thickness) than that of randomly oriented pure DAST powders. This is the first demonstration of such intense SHG radiation and long-range ordering for a thin film sample of a nonlinear organic salt. Furthermore, this work suggests that OVPD represents a general technique for growing thin films of highly polar, nonlinear optical materials such as DAST.

Organic vapor phase deposition: a new method for the growth of organic thin films with large optical non-linearities

We describe a novel technique, organic vapor phase deposition, for the growth of thin films of optically non-linear organic salts. A volatile precursor of each component of the salt is carried as a vapor to a hot-wall reaction chamber by independently controlled streams of carrier gas. The components react to form a polycrystalline thin film on substrates of glass and gold. Excess reactants and reaction products are purged from the system by the carrier gas. As an example, we demonstrate the growth of polycrystalline, optically non-linear thin films of 4′-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) with > 95% purity.

Large-scale MOVPE growth of GaAs and AlGaAs layers

The growth of very large area GaAs and Al x Ga 1− x As epitaxial layers by metal organic vapor phase deposition is reported. Deposition over areas up to 1080 cm 2 on a vertical, three-tiered barrel shaped susceptor was evaluated. Depth profiles of carrier concentration, determined by capacitance-voltage measurements, provided details of growth. Resulting undoped, n-type, and p-type GaAs layers were studied as a function of dopant mole fraction, substrate temperature and distance along the direction of flow of source materials. Deposition of Al x Ga 1− x As, on the other hand, was fixed at 750°C and characterized for thickness and stoichiometry by means of X-ray rocking curves. The distribution, conditions, causes, and means of control for growing multiple epitaxial layers using the system under investigation are discussed. Results of this study demonstrate that the following are realizable: (1) GaAs growth with thickness variations as little as ± 10.0% over most of the active area. (2) Doping uniformity within ± 10% along the direction of gas flow. (3) Aluminum content of Al x Ga 1− x As within ±3.0% over the entire surface. (4) Simultaneous, uniform deposition over ninety 2.5 by 4.5 cm 2 wafers.