Overgrowth Of InP Research Articles

Epitaxial Lateral Overgrowth of InP on Nanopatterned GaAs Substrates by Metal–Organic Chemical Vapor Deposition

Epitaxial lateral overgrowth (ELO) of 1.8-μm InP films was performed on nanopatterned GaAs (001) substrates via metal–organic chemical vapor deposition. Parallel SiO2 trenches with a nano-scale width (∼ 170 nm) and various seed line orientations of [110], [410], [010] and [4–10] were first adopted to optimize the growth in our work. Scanning electron microscopy, atomic force microscopy and double-crystal x-ray diffraction were used to characterize the as-grown InP/GaAs heterostructures. The results reveal that the surface morphology and crystalline quality are strongly affected by the seed line orientations, and both of these parameters are optimized under the orientation of the [4–10] direction. A low average full width at half maximum of 285.1 arcsec and a root mean square surface roughness of 2.95 nm are obtained for the 1.8-μm InP film. To clearly observe the initial coalescence stage during the growth processes, thinner (500 nm) ELO InP films were also grown. We found that the seed line orientation has a significant effect on the lateral growth rate and affects the quality of the final InP/GaAs epilayer.

Defect reduction in epitaxial InP on nanostructured Si (001) substrates with position-controlled seed arrays

Defect reduction in epitaxial InP on nanopatterned exact Si (001) substrates was investigated. Top-down lithography and dry etching were used to define 30nm-wide SiO2 trench openings, with concaves recessed into the Si substrates. Uniformly distributed and position-controlled InP seed arrays were formed by selective area growth. Afterwards, the SiO2 mask was removed and InP overgrowth on the seed arrays proceeded. By localizing defects in the buried Si concaves and promoting defect interactions during the coalescence process, a significant reduction in the x-ray linewidth has been achieved for InP layers grown on the nanopatterned Si as compared to blanket epitaxy. Anisotropic defect distribution in the coalesced InP films was observed and its dependency on seed layer thickness was also studied.

Realization of an atomically abrupt InP/Si heterojunction via corrugated epitaxial lateral overgrowth

A coherent InP/Si heterojunction with an atomically abrupt interface and low defect density is obtained by conducting corrugated epitaxial lateral overgrowth of InP on an engineered (001) Si substrate, with InP seed mesa oriented at 30° from the [110] direction in a hydride vapour phase epitaxy reactor. Ohmic conduction across the InP/Si heterojunction can be achieved.

Improvements in epitaxial lateral overgrowth of InP by MOVPE

Indium phosphide and silicon play important and complementary roles in communications wavelength photonic devices. Realizing high quality coalesced epitaxial lateral overgrown (ELO) InP films on Si could greatly reduce cost and encourage the proliferation of energy efficient photonic integrated circuits in consumer devices. By adjusting a parallel line ELO mask and metalorganic vapor phase epitaxial growth conditions, we have fully coalesced and partially coalesced epitaxial lateral overgrowth of InP on InP substrates and Si substrates having strain relaxed III/V buffer layers, respectively. Extended defects were investigated using transmission electron microscopy and were not found to originate at the coalescence of the nearest neighbor growth fronts for linear parallel growth windows oriented 60° off of [0−11] when using a high V/III ratio of 406. In addition, narrowly separated linear parallel growth windows having a large aspect ratio of 7.5 were seen to inhibit the upward propagation of stacking faults through several neighboring openings. Elimination of these two defect sources would leave primarily the challenge of optimizing the morphology of the overgrown InP as a substantial barrier to achieving coalesced ELO InP of sufficient quality for photonic device applications.

Defect reduction in heteroepitaxial InP on Si by epitaxial lateral overgrowth

Epitaxial lateral overgrowth of InP has been grown by hydride vapor phase epitaxy on Si substrates with a thin seed layer of InP masked with SiO2. Openings in the form of multiple parallel lines as ...

Selective area heteroepitaxy through nanoimprint lithography for large area InP on Si

AbstractThe use of nanoimprint lithography, a low cost and time saving alternative to E‐beam lithography, for growing heteroepitaxial indium phosphide layer on silicon is demonstrated. Two types of patterns on 500 nm and 200 nm thick silicon dioxide mask either on InP substrate or InP seed layer on silicon were generated by UV nanoimprint lithography: (i) circular openings of diameter 150 nm and 200 nm and (ii) line openings of width ranging from 200 nm to 500 nm. Selective area growth and epitaxial lateral overgrowth of InP were conducted on these patterns in a low pressure hydride vapour phase epitaxy reactor. The epitaxial layers obtained were characterized by atomic force microscopy, scanning electron microscopy and micro photoluminescence. The growth from the circular openings on InP substrate and InP (seed) on Si substrate is extremely selective with similar growth morphology. The final shape has an octahedral flat top pyramid type geometry. These can be used as templates for growing InP nanostructures on silicon. The grown InP layers from the line openings on InP substrates are ∼ 2.5 μm thick with root mean square surface roughness as low as 2 nm. Completely coalesced layer of InP over an area of 1.5 mm x 1.5 mm was obtained.The room temperature photoluminescence intensity from InP layers on InP substrate is 55% of that of homoepitaxial InP layer. The decrease in PL intensity with respect to that of the homoepitaxial layer is probably due to defects associated with stacking faults caused by surface roughness of the mask surface. Thus in this study, we have demonstrated that growth of heteroepitaxial InP both homogeneously and selectively on the large area of silicon can be achieved. This opens up the feasibility of growing InP on large area silicon for several photonic applications (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Morphological evolution during epitaxial lateral overgrowth of indium phosphide on silicon

Epitaxial lateral overgrowth of InP from mesh and line openings on masked InP seed layer on Si(0 0 1) wafer is investigated. Coalescence occurred more rapidly from the mesh openings than from the line openings. Lethargic coalescence in the line openings is attributed to the gradual formation of growth retarding boundary planes in the initial stages of growth. Extended growth leads to complete coalescence in both types of openings. The surface roughness of the coalesced layer is inversely proportional to its thickness. Cathodoluminescence studies on the uncoalesced islands show the emergence of facets with orientation-dependent dopant concentration, but reveal no defects, in contrast to the coalesced regions. The latter are relaxed and their dislocation density deduced from panchromatic cathodoluminescence mapping varies from 6×10 6 to 4×10 7 cm −2 depending on the layer thickness; the reduced density at higher thickness indicates partial self annihilation of dislocations. TEM cross-section studies show that most of the threading dislocations originating in the InP seed layer/Si interface are blocked by the mask, but new dislocations are generated. Some of these dislocations are associated with bounding planar defects such as stacking faults, possibly generated during lateral growth across the mask due to unevenness of the mask surface.

Epitaxial lateral overgrowth of InP on Si from nano-openings: Theoretical and experimental indication for defect filtering throughout the grown layer

We present a model for the filtration of dislocations inside the seed window in epitaxial lateral overgrowth (ELO). We found that, when the additive effects of image and gliding forces exceed the defect line tension force, filtering can occur even in the openings. The model is applied to ELO of InP on Si where the opening size and the thermal stress arising due to the mask and the grown material are taken into account and analyzed. Further, we have also designed the mask patterns in net structures, where the tilting angles of the openings in the nets are chosen in order to take advantage of the filtering in the openings more effectively, and to minimize new defects due to coalescence in the ELO. Photoluminescence intensities of ELO InP on Si and on InP are compared and found to be in qualitative agreement with the model.

Heteroepitaxy of InP on Silicon-on-Insulator for Optoelectronic Integration

Epitaxial lateral overgrowth of InP was performed on patterned silicon-on-insulator (SOI) and compared with that on Si substrates in a low pressure hydride vapor phase epitaxy system. The InP was characterized by cathodoluminescence. No red shift of peak wavelength was detected for InP/SOI indicating a negligible thermal strain. Additional low energy peaks were found in some regions with a granular structure on the SOI template. A subsequent growth of an InGaAsP/InP MQW (multi quantum well) structure (λ ~ 1.5 µm) was grown on the SOI template and on a planar InP reference sample by metal- organic phase epitaxy. The MQW was characterized by room temperature photoluminescence. A red shift of 35 nm with respect to the reference sample was attributed to the selective-area effect causing thicker wells and/or an increased indium content. Although the PL intensity was weaker than that obtained for the reference, the FWHMs were comparable.

Surface characterization of epitaxial lateral overgrowth of InP on InP/GaAs substrate by MOCVD

Epitaxial lateral overgrowth (ELO) of InP on InP/GaAs substrates by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) was investigated. The lateral overgrowth InP layers were obtained on the SiO2 masked InP seed layer, which was deposited on the (100) GaAs substrate by the two-step method. The surface characterization of overgrowth InP was dependent on the V/III ratio, the mask width and the growth time. When decreasing the V/III ratio or reducing the mask width respectively, the sidewalls “competition effect” was obviously observed. After a longer time, new (100)-like top surfaces were formatted because of the precursors migrating from the sidewall facets to the (100) top surfaces. The experimental findings will be explained by growth kinetics in conjunction with the different dominant source supply mechanism.

Initial stage of the overgrowth of InP on InAs∕InP(001) quantum dots: Formation of InP terraces driven by preferential nucleation on quantum dot edges

This letter reports on the growth mechanism of the InP cap layer over InAs∕InP quantum dots (QDs) fabricated by metal organic vapor phase epitaxy (MOVPE). QD edges are shown to act as preferential nucleation sites for the InP cap layer, leading to the formation of InP domains around the nanostructures. As∕P exchange reactions are at the origin of the planarization of the top of the QDs under P-rich ambient, thus leading to a final QD height equal to the local thickness of the InP cap layer. The possibility to use As∕P exchange reactions to homogenize the height distribution of MOVPE grown InAs∕InP QDs is discussed on the basis of these observations.

Growth monitoring of GaAsSb:C/InP heterostructures with reflectance anisotropy spectroscopy

Using time-resolved reflectance anisotropy spectroscopy (RAS) we studied in situ the dynamics of surface processes of Sb-covered GaAs(1 0 0) and InP(1 0 0) under metalorganic vapour-phase epitaxy conditions. Both Sb removal during a hydride purge and Sb incorporation during GaAs and InP overgrowth were monitored enabling the investigation of group V exchange reactions. Sb surface layers are found to be much more stable during purge with PH 3 as compared to AsH 3. Estimated activation energies are 2.5 eV for the Sb–P exchange processes and 1.1 eV for the Sb–As exchange reactions. These values reflect the low volatility of Sb compared to other group V adsorbates. During InP overgrowth Sb is rapidly buried at temperatures of 510 °C and below while it is rather persistent on the surface at temperatures of 550 °C and above. This transition indicates the existence of a highly mobile quasi-liquid InSb surface layer at temperatures above its melting point (∼525 °C).

Area-selective epitaxy and epitaxial lateral overgrowth of InP by liquid phase epitaxy on three integral axes

The area-selective epitaxy (ASE) and epitaxial lateral overgrowth (ELO) were performed on {0 0 1}-, {1 1 1}A,B- and {1 1 0}-oriented InP by liquid phase epitaxy at constant growth temperature (450–650°C). The as-grown surface and cross section were investigated by Nomarski interference optical microscope, SEM and confocal laser scanning microscope. From the cross sectional structure, area-selective epitaxy and ELO layers have shown {1 0 0} and {1 1 1}A,B facets on these surface. When compared with three integral axes, the vertical growth rate on {1 1 0} plane is the fastest among the three integral axes. According to the observations of cross sectional shape, the orientation dependence of vertical growth rate was determined to be {1 1 0}>{1 1 1}A,B>{1 0 0} under the present experimental conditions.

Crystallographic orientation dependence of impurity incorporation during epitaxial lateral overgrowth of InP

Temporally resolved epitaxial lateral overgrowth (ELO) of 12 alternating layers of unintentionally-doped and S-doped InP layers has been conducted in a low-pressure hydride vapour phase epitaxy reactor. The growth was conducted in the openings on a (0 0 1) n-InP substrate and oriented along 30° off the [1 1 0] direction. Based on the analysis of the cleaved cross-sections by scanning electron microscopy and scanning capacitance microscopy, an inhomogeneous dopant distribution has been observed within the same ELO layer. This is explained by invoking different bonding configurations exposed to the incorporating dopant atoms in the different emerging planes.

In situ reflectance monitoring of overgrowth of InGaAs gratings in laser diode manufacture

Spectral reflectance measurements of InP overgrowth upon RIE prepared gratings provide for in situ measurements of layer thickness to control the coupling constant (K) of the laser mode to the grating. We show that the use of a commercially available reflectometer utilized on a rotating disk reactor provides growth rate measurements of InP overgrowth of InGaAs gratings with 50% duty cycle as well as patterned gratings. Spectral reflectance (SR) determined thickness has been correlated to post-growth measurements such as cross section SEM and XRAY measurements with good results. SR measurements also provide an optical signature of grating overgrowth that has thermally degraded gratings and grating overgrowth that can lead to low photoluminescence of MQW layers. The results of these measurements are improved process control of grating overgrowth in laser diode manufacture, enabling higher yields.

Buried InAlGaAs-InP waveguides: etching, overgrowth, and characterization

We report on the fabrication and characterization of InP-buried InAlGaAs rectangular core waveguides, LP-MOCVD is used for growth of the InAlGaAs-InP material system and the regrowth of InP. Reactive ion-etching is employed for achieving smooth and precise etch profiles. An efficient procedure for preparing the surface is described that results in homogeneous epitaxial InP overgrowth by preventing re-oxidation of the air-exposed etched surface. The loss characteristics of waveguides with a core layer thickness of 450 nm and widths ranging from 3.5 to 6 μm are investigated at 1.3-μm wavelength. The propagation loss is found to increase from 3 to 10 dB/cm with decreasing core width. Scattering loss caused by residual sidewall roughness is found to be the dominant loss mechanism.

Reactive Ion Etching of InP/InAlGaAs/InGaAs Heterostructures

InAlGaAs in combination with InP, InGaAs, and InAlAs is an attractive material for long wavelength applications. Reactive ion etching of InP/InAlGaAs/InGaAs heterostructures using plasma is systematically investigated and optimization is obtained. The etching process is investigated as a function of radio‐frequency power density and total pressure and its results are characterized in terms of etch rate, surface‐roughness, and etch profile. Etch conditions for the smooth and reproducable etching of Al‐containing heterostructures are reported. The quality of the results achieved is reflected by excellent quality epitaxial InP overgrowth.

Epitaxial lateral overgrowth of InP by liquid phase epitaxy

Epitaxial lateral overgrowth (ELO) of InP has been conducted for the first time by liquid phase epitaxy (LPE). The overgrowth has been studied for seeds in SiO2 of 2.5 to 7 μm width using starlike and parallel patterns. A wide and flat ELO layer was grown on (001) and (111)B oriented substrates at growth temperature between 773 and 873 K. No etch pits were found in the overgrowth regions. For (001) oriented substrates, the seed aligned away from 〈100〉 and 〈110〉 and their equivalent directions brought the maximum overgrowth up to 100 μm whereas the seed aligned adjoining these directions brought almost no overgrowth. On the other hand, for (111)B oriented substrates, the seed aligned away from 〈110〉 and its equivalent directions brought the maximum overgrowth up to 140 μm whereas the seed aligned adjoining these directions brought almost no overgrowth. The maximum ratio of width to thickness of 47 for (111)B ELO layer was obtained. This value is much larger than that of the (001) ELO layer of 17.

Chemical beam epitaxy of InP on planar and non-planar substrates

High purity InP layers have been grown by chemical beam epitaxy (CBE) using H 2 as the carrier gas for transporting the metal alkyl TMI into the growth chamber. InP layers exhibiting Hall mobility as high as 238,000 cm 2/V·s at 77 K and with a peak value of 311,000 cm 2/V·s at 50 K and residual impurity concentration of 6×10 13 cm −3 at 77 K were grown at 500°C using low V/III ratio (2.2) and PH 3 cracking cell temperature of 950°C. These values are the highest mobility values ever reported for InP grown by any molecular beam technique. Selective embedded growth (SEG) of InP and InGaAs was achieved in 2.0 μm deep trenches opened in Si 3N 4 masks on InP substrates. Overgrowth of InP on corrugated InP substrates was also achieved without damaging the surface grating profile.