Low-pressure Organometallic Vapor Phase Epitaxy Research Articles

Quantitative evaluation of enhanced Er luminescence in GaAs-based two-dimensional photonic crystal nanocavities

We evaluate the enhancement of Er luminescence coupled to two-dimensional (2D) photonic crystal (PC) nanocavities by means of photoluminescence measurements and numerical simulations. L3 PC nanocavities are utilized for characterization and evaluation, with GaAs:Er,O grown by low-pressure organometallic vapor phase epitaxy as the active layer. Optical characterization at room temperature demonstrates a 5.8-fold enhancement of Er luminescence due to coupling to the cavity mode of the 2D-PC nanocavities. This enhancement of Er luminescence is supported by a finite-difference time domain simulation where an enhancement of 4.1 times is found, which is in reasonable agreement with the observed experimental results. These results pave the way toward understanding the interaction between cavity modes in PC nanocavities and luminescence from rare-earth elements.

Optically pumped room temperature low threshold deep UV lasers grown on native AlN substrates

We report here an optically pumped deep UV edge emitting laser with AlGaN multiple quantum wells (MQWs) active region grown on AlN substrate by low pressure organometallic vapor phase epitaxy (LP-OMVPE) in a high-temperature reactor. The 21 period Al_0.53Ga_0.47N/Al_0.7Ga_0.3N MQWs laser structure was optically pumped using 193 nm deep UV excimer laser source. A laser peak was achieved from the cleaved facets at 280.3 nm with linewidth of 0.08 nm at room temperature with threshold power density of 320 kW/cm². The emission is completely TE polarized and the side mode suppression ratio (SMSR) is measured to be around 14 dB at 450 kW/cm².

Linear dependency of Al-mole fraction with group-III precursor flows in Al xGa 1−xN (0≤ x≤1) deposition by LP OMVPE

Al x Ga 1− x N/GaN heterostructures (0≤ x≤1) were deposited on (0 0 0 1)-sapphire by low-pressure (20 Torr) organometallic vapor phase epitaxy utilizing a range of group-III precursor and NH 3 flow rates and a deposition temperature of 1050 °C. The Al-mole fraction of Al x Ga 1− x N layers was controlled by variations in the molar flows of triethylgallium ( f TEG) and trimethylaluminum ( f TMA). Characterization by X-ray diffraction confirmed that increasing the f TMA/ f TEG ratio during deposition resulted in increased Al-mole fraction of Al x Ga 1− x N layers. A linear relationship between the experimental Al-mole fraction of Al x Ga 1− x N layers and the group-III precursor flows was obtained if a correction factor γ was introduced such that x= γf TMA/( γf TMA+ f TEG). This correction factor was found to be independent of group-III precursor flows but dependent on NH 3 partial pressure. The value of γ for these experiments decreased from 1.4 to 1.0 when the NH 3 partial pressure was increased from 0.8 to 16.0 Torr during Al x Ga 1− x N deposition. The growth rate of Al x Ga 1− x N layers was found to be a linear combination of the independent AlN and GaN growth rates when equivalent f TMA and f TEG were utilized under the same deposition conditions.

Electronic Properties of GaN Films Grown on TiC Substrates

Crystalline GaN films have been successfully deposited on titanium carbide substrates by low-pressure organometallic vapor-phase epitaxy technique. Low background carrier concentration was verified by capacitance-voltage measurements. Low-temperature photoluminescence measurements indicate that the heteroepitaxial layer has high crystalline quality, as verified by X-ray measurements, and is consistent with low background donor concentration near the film surface.

Surface morphology of ErP layers on InP and Ga 0.52In 0.48P

We have grown ErP on Ga 0.52In 0.48P (001) lattice-matched to GaAs and on InP (001) by low-pressure organometallic vapor phase epitaxy and investigated the surface morphology of ErP layers. Lattice-mismatch in ErP/Ga 0.52In 0.48P/GaAs heterostructures (Δ a / a = − 0.8%) is much less than that of ErP/InP heterostructures (− 4.5%). Extended X-ray absorption fine structure measurement revealed that Er exists in the form of ErP rock-salt structure in both samples. The estimated growth rate of ErP on Ga 0.52In 0.48P is 1.8 ML/h. Our results demonstrate that ErP on Ga 0.52In 0.48P has smaller surface roughness than ErP on InP. Moreover, an ErP layer exists underneath the surface about 2 ML and the surface roughness does not depend on the ErP thickness in the range of our experiments (2.2–13.7 ML).

Effects of growth sequence on atomic level interfacial structures and characteristics of GaInP/GaAs/GaInP double heterostructures grown by low-pressure organometallic vapor phase epitaxy

We have investigated atomic level interface structures and characteristics of GaInP/GaAs/GaInP double heterostructures grown by low-pressure organometallic vapor phase epitaxy. In photoluminescence (PL) measurements, interface-related emission was clearly observed in the sample grown at 580°C, while it disappeared in the sample grown at 540°C. X-ray crystal truncation rod scattering measurement revealed that In atoms distribute significantly in the GaAs layer (∼12ML) when the GaAs-on-GaInP interface is grown at 580°C and the distribution is highly suppressed when grown at 540°C. By insertion of a thin GaInP layer grown at 540°C to the GaAs-on-GaInP interface in GaInP/GaAs/GaInP laser diodes, threshold current densities were much lower and more uniform than those of the diodes with GaAs-on-GaInP interfaces grown at 580°C.

Reduction of oxygen contamination in AlN

High quality AlN thin films were grown by Low Pressure Organometallic Vapor Phase Epitaxy(LP-OMVPE) on sapphire and Si substrates. oxygen contamination in the Al layers can be reduced drastically by fine tuning of the growth parameters, by avoiding O-containing substrates, and by using a cap GaN layer. AlN films grown on Si, exhibiting oxygen concentration levels of [O] ≤ 1019 cm−3, display an X-Ray Diffraction Full Width Half Maximum (FWHM) of 190 arcsec and an extremely sharp near band-edge cathodoluminescence emission at 5.925 eV with FWHM of 30 meV and 5.975 eV (unresolved). (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

AFM observation of OMVPE grown ErP on InP (0 0 1), (1 1 1)A and (1 1 1)B substrates

ErP has been grown on InP (0 0 1), (1 1 1)A and (1 1 1)B substrates by low-pressure organometallic vapor-phase epitaxy. The morphological change with growth temperature has been explored by atomic force microscope. On all the substrates, ErP is grown in island structure. Height and area size of the ErP islands on (1 1 1)A substrate exhibit an obvious dependence on growth temperature. ErP islands grown at 540°C, that is the suitable temperature for ErP formation, gather to step edges to make wires.

Growth sequence dependence of GaAs-on-GaInP interface characteristics in GaAs/GaInP/GaAs structures grown by low-pressure organometallic vapor phase epitaxy

We have investigated interfacial characteristics of lattice-matched GaInP/GaAs heterostructures grown by low-pressure organometallic vapor phase epitaxy with constant and variable growth-temperature sequences. The 77 K photoluminescence (PL) measurements were used to confirm the existence of a lower-bandgap interlayer at the GaAs-on-GaInP interface. In the sample grown at 610 °C with the constant growth-temperature sequence, only a broad peak was observed at the wavelength longer than that expected from either GaInP or GaAs, while the PL spectrum was dominated by the GaAs near-band-edge emission in the sample grown at 550 °C. By inserting a thin 540 °C-grown GaInP layer into the GaAs-on-GaInP interface with the variable growth-temperature sequence, the interface-related PL peak was also suppressed completely.

Er-related luminescence in Er,O-codoped InGaAs/GaAs multiple-quantum-well structures grown by organometallic vapor phase epitaxy

We have grown Er,O-codoped InGaAs/GaAs multiple-quantum-well (MQW:Er,O) structures by low-pressure organometallic vapor phase epitaxy (OMVPE), and investigated their luminescence properties. The MQW structures are designed to emit light at 0.98 μm for direct excitation of Er ions. Degradation of the structures due to introduction of Er and oxygen is not observed in x-ray diffraction patterns. Er ions doped with oxygen exhibit a sharp and well-ordered photoluminescence spectrum predominantly from one kind of Er center (Er-2O center). Photoluminescence excitation measurements on MQW:Er,O and Er,O-codoped GaAs samples reveal that under below-GaAs-band-gap excitation (830–940 nm), the Er-related luminescence is observed only in the MQW:Er,O sample. It indicates that the luminescence originates from Er ions in InGaAs QWs by means of trap-mediated excitation process.

Growth and Performance Study of Aluminum-Free InGaAs/GaAs/InGaAsP Strained Quantum-Well Pump Lasers

The growth of InGaP, InGaAs and InGaAsP epilayers lattice matched to GaAs using the low pressure organometallic vapor phase epitaxy (LP-OMVPE) system was investigated. For the application of erbium-doped fiber amplifiers (EDFAs), the emission wavelength and far-field pattern of the pump laser were designed. The optical and electrical performances of the resultant pump laser were measured.

Effects of GaP Cap Layer Growth on Self-Assembled InAs Islands Grown on GaP (001) by Organometallic Vapor Phase Epitaxy

We have fabricated GaP/InAs islands/GaP structures using various growth sequences for the GaP cap layer, by low-pressure organometallic vapor phase epitaxy (LP-OMVPE). The effects of the growth sequences on the buried InAs islands and the GaP cap layers have been investigated by cross-sectional transmission electron microscopy (TEM). The two-step growth sequence is effective for the growth of GaP cap layers, whereby the first GaP layer is grown at the same temperature as InAs islands and the second GaP layer is successively grown at the optimized growth temperature of GaP. The growth sequence yields good-quality GaP/InAs islands/GaP structures with small InAs islands (15 nm in width and 5 nm in height) and a high-quality GaP cap layer. Droplet heteroepitaxy of GaP cap layers is feasible for the control of the size of buried InAs islands.

Self-assembled InGaAs dots grown on GaP (0 0 1) substrate by low-pressure organometallic vapor phase epitaxy

We have investigated surface morphology of InGaAs on GaP (001) substrate grown by low-pressure organometallic vapor phase epitaxy. By atomic force microscope and cross-sectional transmission electron microscopy observations, it was found that the morphology depended strongly on trimethylindium flow rate ratio (xTMIn) to the total flow rate of group-III sources. In the low xTMIn region, InGaAs was grown in layer-by-layer mode. In the high xTMIn region, on the other hand, dot formation occurred. In this study, we confirmed that Stranski–Krastanow growth mode took place in the sample grown at xTMIn=0.5.

Growth mode transition of InGaAs in OMVPE growth on GaP (001)

We investigated growth of InGaAs with different In compositions on GaP (001) substrates by low-pressure organometallic vapor phase epitaxy (LP-OMVPE). From atomic force microscope (AFM), plan-view transmission electron microscope (TEM), cross-sectional TEM and high-resolution TEM observations, it was found that the growth depended clearly on the ratio of TMIn flow rate to the total flow rate of group-III sources ( x TMIn). In the low x TMIn region, InGaAs grew as a layer. In the high x TMIn region, on the other hand, island formation took place. At x TMIn=0.5, InGaAs islands were formed by the Stranski–Krastanow (S–K) growth mode.

Growth of highly strained GaInAs/GaAs quantum wells for 1.2 μm wavelength lasers

In this paper we present a successful growth of highly strained GaInAs/GaAs quantum wells by low-pressure organometallic vapor-phase epitaxy using tertiarybutylarsine. The transition from uniform to island or dot-like growth mode has been prohibited by carefully choosing the growth condition. Photoluminescence wavelengths of up to 1.2 μm with a FWHM of 23 meV were obtained. We experimentally determined the maximum well thickness for highly strained GaInAs/GaAs QW of good crystal quality and compared our results to critical thickness models. Transmission electron microscopy measurements were used to discuss the degradation mechanism for highly strained GaInAs layers. Also excellent lasing properties of 1.2 μm highly strained GaInAs/GaAs quantum well lasers have been demonstrated.

Aluminum gallium nitride short-period superlattices doped with magnesium

Short-period superlattices consisting of alternating layers of GaN:Mg and AlGaN:Mg were grown by low-pressure organometallic vapor phase epitaxy. The electrical properties of these superlattices were measured as a function of temperature and compared to conventional AlGaN:Mg layers. It is shown that the optical absorption edge can be shifted to shorter wavelengths while lowering the acceptor ionization energy by using short-period superlattice structures instead of bulk-like AlGaN:Mg.

Investigation of the interface roughness in a LPOMVPE grown AlAs/GaAsmultilayer

Characteristics of the interface roughness in a low-pressure organometallic vapour phase epitaxy (LPOMVPE) grown AlAs/GaAs multilayer are studied by grazing-incidence x-ray scattering. Quantitative results are obtained by comparing experimental and theoretically calculated diffuse scattering maps. These corroborate with the features resolved by atomic force microscopy. The observed morphological features are discussed in the following sections.

Photoreflectance study of InP/InGaAs(1–5 ML)/InP single quantum well

Room-temperature photoreflectance (PR) measurements were successfully used to investigate optical transition energies in InP/InGaAs(1–5 ML)/InP single quantum wells (SQWs) grown by low-pressure organometallic vapor phase epitaxy (OMVPE). PR features due to subband transitions were clearly observed even in the SQWs of extremely thin well thicknesses. PR spectra showed e(1)-hh(1) and e(1)-lh(1) transitions in the InGaAs wells together with the band-to-band transition in the InP layers. Clear PR spectra indicate excellent optical quality of these OMVPE-grown structures. The transition energies were determined by fitting the PR spectra to the theoretical line-shape expression. The resultant e(1)-hh(1) transition energies were equal to energy positions of emission peaks observed in photoluminescence measurements at room temperature. The e(1)-hh(1) and e(1)-lh(1) transition energies decreased with increasing well thicknesses. The behavior agreed qualitatively with the theoretical prediction, although there is a significant discrepancy in transition energies.

Planar selective regrowth of high resistivity semi-insulating InP(Fe) by LP-MOVPE for buried lasers using TBP

Selective planar regrowth of high resistivity (as high as 10 9 Ω cm) Fe-doped semi-insulating InP epitaxial layers has been studied to fabricate current confining layers for buried heterostructure lasers. The epitaxial layers were grown on patterned, nonplanar heterostructure mesa by low-pressure organometallic vapor phase epitaxy (LP-MOVPE) with tertiarybutylphosphine (TBP), trimethylindium (TMI) and iron dicyclopentadienyle (Fe(C 5H 5) 2) as the reactant gases. The shape of the growth around masked mesas without any overhang of the mask has been studied as a function of both the growth conditions and the mesa height. Finally, an optimization of the growth conditions has been performed to planarize ridges as high as 2 μm, the layer quality being characterized by SEM.

Nanometer-scale InAs islands grown on GaP (001) by organometallic vapor phase epitaxy

We have successfully grown nanometer-scale InAs islands on GaP (001) by low-pressure organometallic vapor phase epitaxy (LP-OMVPE). Effects of substrate temperature and InAs deposition rate on the shape, size and areal density of InAs islands were investigated by ex-situ atomic force microscope (AFM) and high-energy electron diffraction (HEED). The AFM observations showed that the island size decreased with the substrate temperature while the areal density increased, indicating that migration play a role on island formation. The HEED patterns provided significant result that the island grown at high temperature (650°C) consisted of a few grains, while the island grown at low temperatures (550 and 500°C) was single crystalline.