High quality Ge thin film grown by ultrahigh vacuum chemical vapor deposition on GaAs substrate

Tang, Shih Hsuan; Chang, Edward Yi; Hudait, Mantu K.; Maa, Jer‐Shen; C, Liu; Luo, Guang Li; Trinh, Hai Dang; Su, Yung Hsuan

doi:10.1063/1.3580605

Cited by 33 publications

(16 citation statements)

References 11 publications

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“…We also measured the ultraviolet photoelectron spectrum of the sample and determined the absorption onset that gives a take-off energy of 0.66 eV above the Fermi level, which corresponds to the valance band edge (SI, Figure S9). The shift from the bulk value of 0.16 eV [38] is consistent with the bandgap evaluated from UV-vis-NIR data and quantum confinement effects. The TEM images of the sample show crystalline Ge nanoparticles with an average particle size of about 3.0-5.0 nm, which is consistent with the size obtained from the electronic band-gap value.…”

Section: Resultssupporting

confidence: 85%

Synthesis of Nanoamorphous Germanium and Its Transformation to Nanocrystalline Germanium

Dag

Henderson

Ozin

2012

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A simple reaction between a mild reducing agent such as a trialkoxysilane and GeIV species such as germanium tetraalkoxides in a room‐temperature water/alcohol solution produces silica‐coated ultrasmall (2–3 nm) amorphous germanium nanoparticles (na‐Ge/SiO2). The initial reaction involves the straightforward hydrolysis and condensation of the precursors, Ge(OCH2CH3)4 and (CH3CH2O)3SiH, where the reaction rate depends on the water concentration in the reaction medium. These processes can be further accelerated by adding acid to the reaction medium or carrying out the reaction at higher temperatures. At low water contents (up to 50% water/ethanol) and low acid concentrations, the reaction proceeds as a clear solution, and no precipitation is observed. The initially colorless clear solution progressively changes to pale yellow, yellow, orange, red, and finally dark red as the na‐Ge particles grow. Evaporation of the solvent yields a reddish‐brown powder/monolith consisting of na‐Ge, embedded in an encapsulating amorphous silica matrix, na‐Ge/SiO2. The formation of na‐Ge proceeds extremely slowly and follows a first‐order dependence on both water concentration and diameter of the na‐Ge particles under the reaction conditions used. Annealing of the na‐Ge/SiO2 powder under an inert atmosphere at 600 °C produces ultrasmall germanium nanocrystals (nc‐Ge) embedded in amorphous silica (nc‐Ge/SiO2). Freestanding, colloidally stable nc‐Ge is obtained by chemical etching of the encapsulating silica matrix.

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Section: Resultssupporting

confidence: 85%

Synthesis of Nanoamorphous Germanium and Its Transformation to Nanocrystalline Germanium

Dag

Henderson

Ozin

2012

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“…Heteroepitaxy of GaAs/Ge(001) is more complex compared to Ge on (001)GaAs due to polar-on-nonpolar epitaxy. The RHEED studies indicate a basic difference in growth morphology between the growth of GaAs and that of Ge on the polar (100) surface: the growth of Ge on GaAs results in a smooth surface, [41][42][43] whereas the growth of GaAs on Ge produces a rough surface on an atomic scale as observed by several researchers. 39,55 The observed difference is explained due to an inherent difference in MBE growth mechanism between a compound semiconductor, GaAs, and an elemental semiconductor, Ge.…”

Section: Resultsmentioning

confidence: 63%

“…Although, several groups succeeded in growing highquality Ge epitaxial layer on GaAs 19,26,27,[33][34][35][36][37][38][39][40][41][42][43] and GaAs/Ge/ GaAs heterostructures, 44,45 however, these work suffer from the interdiffusion of elements 46 and arsenic (As) contamination in the Ge layer due to the Ge and III-V material growth carried out in a single molecular beam epitaxy (MBE) chamber 34,47 or metal-organic vapor-phase epitaxy chamber. 42 This results in excess As point defects, which nucleate dislocation loops during the growth of GaAs overlayer on Ge.…”

Section: Introductionmentioning

confidence: 99%

In situ grown Ge in an arsenic-free environment for GaAs/Ge/GaAs heterostructures on off-oriented (100) GaAs substrates using molecular beam epitaxy

Hudait

Zhu

Jain

et al. 2012

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

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High-quality epitaxial Ge layers for GaAs/Ge/GaAs heterostructures were grown in situ in an arsenic-free environment on (100) off-oriented GaAs substrates using two separate molecular beam epitaxy (MBE) chambers, connected via vacuum transfer chamber. The structural, morphological, and band offset properties of these heterostructures are investigated. Reflection high energy electron diffraction studies exhibited (2 Â 2) Ge surface reconstruction after the growth at 450 C and also revealed a smooth surface for the growth of GaAs on Ge. High-resolution triple crystal x-ray rocking curve demonstrated high-quality Ge epilayer as well as GaAs/Ge/(001)GaAs heterostructures by observing Pendell€ osung oscillations and that the Ge epilayer is pseudomorphic. Atomic force microscopy reveals smooth and uniform morphology with surface roughness of $0.45 nm and room temperature photoluminescence spectroscopy exhibited direct bandgap emission at 1583 nm. Dynamic secondary ion mass spectrometry depth profiles of Ga, As, and Ge display a low value of Ga, As, and Ge intermixing at the Ge/GaAs interface and a transition between Ge/GaAs of less than 15 nm. The valence band offset at the upper GaAs/Ge-(2 Â 2) and bottom Ge/(001)GaAs-(2 Â 4) heterointerface of GaAs/Ge/GaAs double heterostructure is about 0.20 eV and 0.40 eV, respectively. Thus, the high-quality heterointerface and band offset for carrier confinement in MBE grown GaAs/Ge/GaAs heterostructures offer a promising candidate for Ge-based p-channel high-hole mobility quantum well field effect transistors. V

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“…A number of reports refer to an enhancement of luminescence from Ge direct band gap with increasing temperature, 18-20 including Sun's recent work on PL on Ge-on-Si, 10 and more recently published work by Tang et al that reported on the luminescence properties of Ge grown on GaAs by UHVCVD. 21 Sun's work also showed that n-type doping can be used to significantly enhance luminescence from the Ge direct band gap 10 because n-type doping raises the Fermi-level and increases the probability for electrons occupying states in the direct C valley, increasing the probability of direct band gap transitions from Ge at room temperature.…”

Section: Microstructural Characterization and Photoluminescence Of Gementioning

confidence: 99%

Photoluminescence and secondary ion mass spectrometry investigation of unintentional doping in epitaxial germanium thin films grown on III-V compound by metal-organic chemical vapor deposition

Bulsara¹,

Fitzgerald²

2012

Journal of Applied Physics

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High quality epitaxial germanium (Ge) thin films grown on lattice matched and mismatched III-V compound may lead to development of new electronic and optoelectronic devices. Understanding the doping and electronic properties of these Ge thin films is the first step in this development. In this paper, we report on high-quality epitaxial Ge thin films grown on GaAs and AlAs by metal-organic chemical vapor deposition. Cross-sectional transmission electron microscopy and atomic force microscopy reveal the high structural quality of the Ge thin films. Using photoluminescence, secondary ion mass spectrometry, and spreading resistance analysis, we investigated the unintentional doping characteristics of the fabricated Ge-on-III-V thin films. We found that arsenic (n-type doping) concentration is determined by the background partial pressure of volatile As-species (e.g., As 2 and As 4 ), which incorporate into the Ge thin films via gas phase transport during the growth. Group III element (p-type doping) incorporation in the Ge thin films occurs during the growth through a surface exchange process. There exists a trade-off between Ge film structural quality and group III element "auto-doping." III-V compound surfaces that are group III element-rich facilitate the initiation of Ge thin films with high crystalline quality and low surface roughness. However, the group-III-rich surfaces also result in high group III element (p-type doping) concentrations in the Ge thin films.

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High quality Ge thin film grown by ultrahigh vacuum chemical vapor deposition on GaAs substrate

Cited by 33 publications

References 11 publications

Synthesis of Nanoamorphous Germanium and Its Transformation to Nanocrystalline Germanium

Synthesis of Nanoamorphous Germanium and Its Transformation to Nanocrystalline Germanium

In situ grown Ge in an arsenic-free environment for GaAs/Ge/GaAs heterostructures on off-oriented (100) GaAs substrates using molecular beam epitaxy

Photoluminescence and secondary ion mass spectrometry investigation of unintentional doping in epitaxial germanium thin films grown on III-V compound by metal-organic chemical vapor deposition

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