Thickness dependence of material quality in GaAs-on-Si grown by metalorganic chemical vapor deposition

Epitaxial layers of GaAs on (100) GaAs substrates can be grown by close-spaced vapor transport using water vapor as the transporting agent. The parameters for the transport are Ti = 755°C. AT' = 45°C. and 6 = 0.03 cm (where Ti is the temperature of the graphite heating the substrate; AT', the temperature difference between the graphite heating the source and the one heating the substrate; and 6. the thickness of the spacer separating the GaAs source and the substrate). Mirrorlike epitaxial layers of GaAs are obtained with these parameters when water vapor, at a partial pressure of 4.58 Torr ( 1 Torr = 133.3 Pa), is introduced with H, at the beginning of the temperature rise of the reactor. The dimensions of the epitaxial layer are only limited by the size of the reactor. Using the same growth conditions. it is not possible to obtain mirrorlike films of GaAs on (100) Ge substrates. Instead, the layers are dull grey (sample no. I ) . It is howcder not a polycrystalline deposition since the pole figures, obtained by X-ray diffraction. reveal only four crystallographic orientations: {loo} the main one. {221} the secondary one, and {021} + {I 12) two minor contributions. Mirrorlike films of GaAs on (100) Ge substrates of less than 1 cni' have been obtained with T: = 775OC. AT' = 25°C. and 6 = 0.03 cm. With these conditions, the growth rate is 0.25 + 0.08 k m m i n I . The time evolution of T: and AT', froni room temperature up to the equilibrium temperature also influences the surface morphology of GaAs films on Ge while this was not the case for GaAs films on GaAs substrates. When the Ge substrate is larger than I cm'. the centre of the film becomes textured but the edges reniain mirrorlike (sample no. 2). Pole figures obtained for the center and the edges of sample no. 2 are similar. They are characterized by one large diffraction due to the (100) orientation. A few random crystallographic orientations and sometimes the {221} orientation, however, bearly emerge froni the background of these pole figures. Also transmission electron microscopy does not reveal any major difference between the center and the edges of sample no. 2. The density of threading dislocations is the sanie for both regions, varying from 10' c m ', close (2-3 k m ) to the interface, to lo7 c m ' in the thickness of the film. No misfit dislocations were observed.Antiphase boundaries are present in both regions as well. The only difference between the centre and the edges of sample no. 2 involves microtwin bundles: in the center region, there are two microtwin bundles per micrometre of interface, extending up to 6 km in the GaAs film while on the edges, there is one bundle per micrometre with an extension of only one micrometre into the epitaxial layer. Mirrorlike GaAs films can be obtained on (100) Ge substrates of at least 1 in ( 1 in = 2.5 cni) in diameter by increasing 6 to 0.2 cm and by injecting water vapor in the reactor only when Ti reached 650°C: the other deposition parameters reniain the sanie as for sample no. 2. In these conditions, th...

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“…Similar defects have been described by Pearton er al. (23). They start at the interface and vanish inside the GaAs film.…”

Section: Tem Characterizationmentioning

confidence: 97%

Growth by the CSVT (close-spaced vapor transport) technique and characterization of epitaxial GaAs layers on Ge substrates

Koskiahde¹,

Cossement²,

Guelton³

et al. 1991

Can. J. Phys.

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“…However, growing a high-quality GaAs epilayer on an Si substrate is difficult because it exhibits a large lattice mismatch and quite different thermal expansion coefficients. Accordingly, GaAs epilayers grown directly on Si substrates usually had a dislocation density of over 10 8 cm À2 [1,2]. Otherwise, the influence of dislocation density on the performance of the GaAs-on-Si solar cell has been theoretically analyzed [3], suggesting that the dislocation density of GaAs on Si must be lower than 5 Â 10 5 cm À2 to yield an energy conversion efficiency that is equivalent to those of GaAs-on-GaAs and InP-on-InP solar cells.…”

Section: Introductionmentioning

confidence: 99%

Heteroepitaxial growth of GaAs on Si by MOVPE using a-GaAs/a-Si double-buffer layers

Uen

Huang

et al. 2006

Journal of Crystal Growth

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“…Because of the large lattice mismatch ($4%) between GaAs and Si, it is difficult to obtain metamorphic GaAs/Si wafers with very low dislocation density and root mean square (RMS) roughness through two-step growth only. 3,4 Therefore, several auxiliary methods such as postannealing, 5,6 thermal-cycle annealing (TCA), 7-9 and strained-layer superlattices [8][9][10][11] have been put forward and combined with two-step growth. To the best of our knowledge, the lowest RMS roughness values thus far is 1.2 nm in a 2 Â 2 lm 2 scanning area for a 3-lm-thick GaAs epilayer grown by MBE (Ref.…”

Section: Introductionmentioning

confidence: 99%

Three-step growth of metamorphic GaAs on Si(001) by low-pressure metal organic chemical vapor deposition

Wang

Jia

et al. 2013

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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In this study, metamorphic growth of GaAs on Si(001) substrate was investigated via three-step growth in a low-pressure metal organic chemical vapor deposition reactor. Three-step growth was achieved by simply inserting an intermediate temperature GaAs layer between the low temperature GaAs nucleation layer and the high temperature GaAs epilayer. Compared with conventional two-step growth, three-step growth could further reduce surface roughness and etch pit density. By combining three-step growth with thermal-cycle annealing, the authors have grown a 1.8-μm-thick GaAs epilayer with root mean square roughness of only 1.8 and 0.73 nm in 10 × 10 μm2 and 2 × 2 μm2 scanning areas, respectively. The threading dislocation density of the 1.8-μm-thick GaAs epilayer was as low as 1.1 × 107 cm−2, as calculated directly from the double crystal x-ray diffraction ω-scan full width at half maximum of the GaAs diffraction peak. The corresponding etch pit density was only 3 × 106 cm−2.

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Thickness dependence of material quality in GaAs-on-Si grown by metalorganic chemical vapor deposition

Cited by 41 publications

References 28 publications

Growth by the CSVT (close-spaced vapor transport) technique and characterization of epitaxial GaAs layers on Ge substrates

Growth by the CSVT (close-spaced vapor transport) technique and characterization of epitaxial GaAs layers on Ge substrates

Heteroepitaxial growth of GaAs on Si by MOVPE using a-GaAs/a-Si double-buffer layers

Three-step growth of metamorphic GaAs on Si(001) by low-pressure metal organic chemical vapor deposition

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