Pressure Organometallic Chemical Vapor Research Articles

Organometallic Chemical Vapor Deposition Growth of Heterostructure of Wide Band Gap and Transparent Boron Phosphide on Silicon

A boron phosphide (BP) layer was grown on the (111) Si substrate by atmospheric pressure organometallic chemical vapor deposition (MOCVD) using triethylboran ((C2H5)3B) and phosphine (PH3) sources. By transmission electron diffraction analysis, the transparent BP layer was found to grow on (111) Si with the following orientation: (111),<110>-Si//(111),<110>-BP. The MOCVD-grown BP layers exhibited transparency under fluorescent light illumination. Reflected light color was observed to vary depending on the thickness of the BP layer. The refractive index (n) of the heteroepitaxial (111) BP layer was revealed to decrease from 3.16 at a wavelength (λ) of 350 nm to 2.77 at λ of 750 nm. The extinction coefficient (k) corresponding to n at λ of 350 nm was 0.19. Refractive index (n) and k at λ of 350 nm gave 9.95 as the real part of the complex dielectric constant of the MOCVD-grown BP layer. The optical evaluation indicated that BP is applicable as a transparent III-V semiconductor layer for forming heteroepitaxial structures with Si.

Amorphous TiO 2 in LP-OMCVD TiN xO y thin films revealed by XPS

TiN(O)–TiO 2 thin films were prepared on Si(1 0 0) by the low pressure organo metallic chemical vapor deposition (LP-OMCVD) method, using ammonia and titanium isopropoxide as precursors. In order to complete previous characterizations, an Ar + bombardment/XPS coupled study was carried out. This method is based on the fact that the behavior of a compound towards an ion bombardment is a function of its composition. In particular, Ar + bombardment of TiO 2 (whatever its form) leads to a preferential sputtering of oxygen atoms with subsequent reduction of titanium and formation of Ti 3+ and Ti 2+ easily detectable by XPS from a significant broadening of the Ti 2p lines. In the opposite, no broadening of the Ti 2p lines is observed for an Ar + bombardment of TiN. Then, with this method, we succeed in showing that films obtained at high temperature (≥700°C) contain only a TiN x O y phase which is isomorphic to TiN. In the coatings, synthesized at low temperatures (≤650°C) amorphous TiO 2 has been evidenced.

Effects of growth interruption on the optical properties of AIGaAs/GaAs and GaAs/InGaAs quantum wells grown by atmospheric pressure organometallic chemical vapor deposition

In this study, the effects of growth interruptions on Al0.17Ga0.83As/GaAs and GaAs/ InxGa1-xAs quantum wells (QWs) grown by organometallic chemical vapor deposition (OMCVD) were assessed using low-temperature photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. Growth interruption times were varied between 60, 10, and 0 sec. For both material systems, as the interruption time was reduced, the ground-state QW transition energies increased, while the linewidths of the peaks decreased. For the Al0.17Ga0.83As/GaAs structures, 5 K PL data suggests that the incorporation of impurities is enhanced by longer growth interruption times. In addition, as the interruption time was reduced, the energy separation between the 5 K PL and PLE peaks (Stokes shift) decreased, and was as low as 2.6 meV for no interruption. For GaAs/In0.11Ga0.89As samples, 2 K PL data indicated that the incorporation of donor species was not a function of the growth interruption time.

Effect of growth rate on the band gap of Ga0.5In0.5P

The band gap of Ga0.5In0.5P is reported as a function of growth rate and growth temperature. The Ga0.5In0.5P is grown lattice matched to 2°-off (100) GaAs substrates by atmospheric pressure organometallic chemical vapor deposition using an inlet group V/III ratio of 65. The variation of the band gap is surprisingly complex, taking five different functional forms within the two-dimensional parameter space. These include regions in which the band gap (1) increases with growth rate, (2) decreases with growth rate, (3) is independent of both growth rate and temperature, (4) is independent of growth rate, but dependent on growth temperature, and (5) is not measurable since three-dimensional, instead of two-dimensional, growth is observed. The behavior can only be explained by a theory involving competing processes. One such theory is described.

Critical thickness of GaAs/InGaAs and AlGaAs/GaAsP strained quantum wells grown by organometallic chemical vapor deposition

In this paper we describe a study of strained quantum wells (QWs) as a means to experimentally observe the critical thickness (hc) for the formation of interfacial misfit dislocations. Two material systems were investigated: GaAs/In0.11Ga0.89As, in which the QW layers are under biaxialcompression, and Al0.35Ga0.65As/GaAs0.82P0.18, in which the QW layers are under biaxialtension. Samples were grown by atmospheric pressure organometallic chemical vapor deposition, and characterized by low-temperature photoluminescence (PL), x-ray diffraction, optical microscopy, and Hall measurements. For both material systems, the observed onset of dislocation formation agrees well with the force-balance model assuming a double-kink mechanism. However, overall results indicate that the relaxation is inhomogeneous. Annealing at 800–850° C had no significant effect on the PL spectra, signifying that even layers that have exceededhc and have undergone partial relaxation are thermodynamically stable against further dislocation propagation.

Kinetic limits to growth on (001) and (110) GaAs by OMCVD

This paper summarizes results of our investigations of growth on (001) and (110) GaAs by atmospheric pressure organometallic chemical vapor deposition (OMCVD). We follow evolutions of surface species to a sensitivity of 0.01 monolayer (ML) on a time scale of 0.1 s under alternating flows of trimethylgallium (TMG) and arsine (AsH 3) as functions of partial pressure, sample temperature, and surface orientation. The reaction of TMG with an AsH 3-saturated (001) surface is rate-limited by competition between desorption and decomposition of TMG molecules chemisorbed to surface lattice sites via an exclude-volume mechanism, while the reaction of AsH 3 with the TMG-saturated (001) surface is essentially instantaneous. In contrast, TMG reacts essentially instantaneously with the AsH 3-saturated (110) surface while the AsH 3 reaction with the TMG-saturated (110) surface is the rate-limiting step. However, the latter rate is not intrinsic to the AsH 3-surface reaction but appears to be determined by desorption of adsorbed species that block active sites.

Critical Thickness of GaAs/InGaAs and AlGaAs/GaAsP Quantum Wells Grown by Atmospheric Pressure OMCVD

AbstractA critical layer thickness study of strained GaAs/InGaAs and AlGaAs/GaAsP quantum wells (QWs) grown by atmospheric pressure organometallic chemical vapor deposition (OMCVD) is reported. Characterization by conventional photoluminescence (PL), photoluminescence excitation (PLE) spectroscopy, optical microscopy, and x-ray diffraction suggests that partial or regional relaxation begins to occur at critical thicknesses predicted by the force-balance model. To test the stability of strained quantum wells with well width near or exceeding the predicted critical thickness, annealing up to 850°C for ten minutes was carried out. No sign of degradation or complete relaxation of the QW layers was observed.

Tailoring of hole eigenenergies in strained GaAsP/AlGaAs single quantum wells grown by atmospheric pressure organometallic chemical vapor deposition

In this letter we present experimental results demonstrating the effects of tensile strain on the ground-state hole eigenenergies of strained GaAsP/AlGaAs quantum wells (QWs) grown by organometallic chemical vapor deposition. Low-temperature photoluminescence (PL) spectra exhibit sharp, intense peaks corresponding to the n=1 heavy and light hole related QW transitions. The relative positions of the peaks depend on both the strain and the width of the QWs. In wider wells (120 Å), the lowest energy, and dominant PL peak was assigned to the light hole, and for a 80 Å well, the heavy and light hole peaks merged.

Exciton photoluminescence linewidths in very narrow AlGaAs/GaAs and GaAs/InGaAs quantum wells

A study of the low-temperature photoluminescence characteristics of very narrow one-dimensional quantum-well structures, grown by atmospheric pressure organometallic chemical vapor deposition, is presented. Theoretically predicted narrowing of photoluminescence peaks as quantum-well widths approach zero was experimentally observed in both AlGaAs/GaAs and strained GaAs/InGaAs samples. The role of such data in determining interface microstructure is discussed.

Pseudomorphic GaAs/InGaAs single quantum wells by atmospheric pressure organometallic chemical vapor deposition

High-quality pseudomorphic GaAs/In0.12Ga0.88As single quantum wells (QW’s) were prepared by atmospheric-pressure organometallic chemical vapor deposition. Photoluminesence spectra measured at 2.5 and 78 K exhibit intense, sharp peaks [full width at half-maximum (FWHM)=2.6 meV for a 17-Å well at 78 K] from the quantized energy transitions of the QW’s. Peak positions agree well with a square well calculation that includes the strain-induced band-gap shift in the In0.12Ga0.88As. Quite unlike previous work with QW’s in which the FWHM was found to exponentially increase with decreasing well width, we observed a narrowing of the QW signals as the well width went below ∼30 Å. In larger well samples (300 Å), the onset of surface crosshatch patterns was observed, which is expected from critical thickness theory.

High gain InP/InGaAs heterojunction bipolar transistors grown by OMCVD

Atmospheric pressure organometallic chemical vapor deposition has been used to grow InP/GaInAs heterojunction bipolar transistors from trimethylgallium, trimethylindium, arsine and phosphine sources. The doping characteristics of the layers comprising the device has been studied using diethylzinc and diethyltelluride as the dopants. It is shown that both Zn and Te, while behaving nearly ideally in GaInAs, exhibit anomalous behavior in InP. In spite of this, InP/GaInAs heterojunction bipolar transistors with gains as high as 5000 have been fabricated. The estimated minority carrier diffusion length in the base is 7.5 μm which indicates that the GaInAs is of extremely high quality.

Selective Area Growth of High Quality GaAs by OMCVD Using Native Oxide Masks

A study of selective area growth by atmospheric pressure organometallic chemical vapor deposition (OMCVD) using plasma‐grown native oxide masks was conducted. Deposition experiments were carried out with different growth parameters to observe the variation of polycrystalline coverage on the oxide mask. With high growth temperatures or low V/III ratios, poly deposition on the mask was depleted, particularly in regions near the unmasked single‐crystal areas. With the optimum conditions for growth, the polycrystalline growth was homogeneous to the single‐crystal boundary, and the single‐crystal areas exhibited liquid nitrogen mobilities up to 105,000 cm2/Vs. Etch‐and‐fill experiments were also performed using a based etch to obtain near vertically etched sidewalls. Growth from the walls caused little distortion at the edges of the filled pockets and flat single‐crystal surfaces were obtained.

AlGaAs/GaAs quantum wells with high carrier confinement and luminescence efficiencies by organometallic chemical vapor deposition

Single and multiple quantum wells with well widths ranging from 10 to 135 Å were grown by atmospheric pressure organometallic chemical vapor deposition and characterized by photoluminescence (PL) and electrical measurements. Compared with single layers of high-purity GaAs and AlGaAs which have high intensity near band-edge excitonic transitions, the quantum well (QW) structures exhibit very strong luminescence of the discrete QW eigenstates. The intense QW signals indicate that the carrier confinement efficiency of the wells is very high, which is also supported by significant mobility enhancement in the samples. The sharp PL lines suggest high quality and smoothness of the well interfaces.

Alternatives to arsine: The atmospheric pressure organometallic chemical vapor deposition growth of GaAs using triethylarsenic

Studies on the homoepitaxial growth of unintentionally doped GaAs by atmospheric pressure organometallic chemical vapor deposition using triethylarsenic and trimethylgallium have been carried out, and the effects of growth temperature, V/III ratio, and flow rate on film characteristics are reported. Mirrorlike epitaxial layers of n-type GaAs were obtained at substrate temperatures of 540–650 °C and at V/III ratios of 6.7–11. The carrier concentrations for these films were approximately 1016–1017 cm−3, and from secondary ion mass spectroscopic analysis, the predominant epilayer impurities were determined to be both carbon and silicon.