Tunneling microscopy of point defects on GaAs(110)

Lengel, G.

doi:10.1116/1.586915

Cited by 56 publications

(38 citation statements)

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“…Here, a dark contrast on an array of about 3 ϫ 3 missing unoccupied dangling bonds has been interpreted as the signature of a Ga vacancy. 7 That signature does not agree with the signature of the complex, but we suggest that signature to be caused by hydrogen adsorption. 31 Another group interpreted the X-shaped dark contrast to be the signature of a Ga vacancy.…”

Section: Simulated Stmmentioning

confidence: 54%

“…[1][2][3][4][5][6] In contrast to the anion vacancy, there are only a few studies of cation vacancies. In scanning tunneling microscopy ͑STM͒ images of the unoccupied states of GaAs ͑110͒ surfaces, two features interpreted as being caused by Ga vacancies have been reported: Lengel et al 7 observed a dark contrast that appears on an array consisting of about 3 ϫ 3 missing unoccupied dangling bonds, whereas Ebert and Urban 8 and Domke et al 9 observed an X-shaped dark contrast consisting of one missing unoccupied dangling bond.…”

Section: Introductionmentioning

confidence: 99%

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Breakdown of cation vacancies into anion vacancy-antisite complexes on III-V semiconductor surfaces

et al. 2008

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An asymmetric defect complex originating from the cation vacancy on ͑110͒ III-V semiconductor surfaces which has significantly lower formation energy than the ideal cation vacancy is presented. The complex is formed by an anion from the top layer moving into the vacancy, leaving an anion antisite-anion vacancy defect complex. By calculating the migration barrier, it is found that any ideal cation vacancies will spontaneously transform to this defect complex at room temperature. For stoichiometric semiconductors the defect formation energy of the complex is close to that of the often-observed anion vacancy, giving thermodynamic equilibrium defect concentrations on the same order. The calculated scanning tunneling microscopy ͑STM͒ plot of the defect complex is also shown to be asymmetric in the ͓110͔ direction, in contrast to the symmetric one of the anion vacancy. This might therefore explain the two distinct asymmetric and symmetric vacancy structures observed experimentally by STM.

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Section: Simulated Stmmentioning

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Breakdown of cation vacancies into anion vacancy-antisite complexes on III-V semiconductor surfaces

et al. 2008

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“…14 The currently published experimental values for the screening length ͑which determines the extend of the screened Coulomb potential͒ at GaAs and InP͑110͒ surfaces are constantly between 1 and 2 nm independent of the defect and doping concentrations investigated. [9][10][11][12][13][14] This disagrees with theoretical expectations, which predict a strong increase in the screening length with decreasing carrier concentration. Despite theoretical efforts to clarify this inconsistency by assuming additional screening by defect-induced carriers at the surface, 7,8 no understanding of the apparently short screening length at negligibly low defect concentrations was achieved.…”

Section: Introductionmentioning

confidence: 84%

“…First, the screening potentials are frequently approximated by height profiles taken in constant-current STM images. [9][10][11][12][13][14] Second, the close proximity of the STM tip near the surface induces localized band bendings, [15][16][17][18] which modify the potential around charged defects significantly and thus the screening cannot be probed quantitatively. Third, the limited signal to noise ratio of barrier height or surface photovoltage measurements [19][20][21] restrict a quantitative data analysis.…”

Section: Introductionmentioning

confidence: 99%

Three- to two-dimensional transition in electrostatic screening of point charges at semiconductor surfaces studied by scanning tunneling microscopy

2009

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The electrostatic screening of localized electric charges on semiconductor surfaces is investigated quantitatively by statistically analyzing the spatial distribution of thermally formed positively charged anion surface vacancies on GaAs and InP͑110͒ surfaces. Two screening regimes are found: at low vacancy concentrations the vacancy charges are found to be three-dimensionally screened by bulk charge carriers. The corresponding screening length, which increases strongly with decreasing carrier concentration, is best described by the classical bulk screening length evaluated with a surface dielectric constant. With increasing vacancy concentration at given bulk carrier concentration, a three-to two-dimensional screening transition occurs. At high vacancy concentrations, the screening is found to be governed by charge carriers located in a two-dimensional surface vacancy defect band, which is partially filled due to the vacancy-induced surface band bending.

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“…Up to date, As vacancies have been reported in GaAs [21][22][23] and InAs [24], P vacancies in InP [25][26][27] and GaP [26,28], Sb vacancies in InSb [29,30], and Ga vacancies in GaAs [22,31,32] and GaP [33] (110) surfaces. Recently, vacancies have also been observed in CdSe and CdS cleavage surfaces [34].…”

Section: Observation Of Surface Vacancies With Atomic Resolutionmentioning

confidence: 99%

Defects in III-V semiconductor surfaces

Ebert

2002

Applied Physics A: Materials Science & Processing

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Abstract. This work reports the measurement of the nanoscale physical properties of surface vacancies and the extraction of the types and concentrations of dopant atoms and point defects inside compound semiconductors, primarily by crosssectional scanning tunneling microscopy on cleavage surfaces of III-V semiconductors. The results provide the basis to determine the physical mechanisms governing the interactions, the formation, the electronic properties, and the compensation effects of surface as well as bulk point defects and dopant atoms. 71.55.Eq; 73.20.Hb; 68.37.Ef The electrical properties of semiconductors and thus their applicability in electronic devices are to a large degree governed by defects and dopant atoms incorporated during growth and production processes. Although some defects and dopant atoms may be desired to achieve the optimum device properties, other defects may be formed unintentionally and counteract the desired electronic properties. Therefore, considerable research efforts were focussed on determining the nanoscale physics governing the formation of point defects, the incorporation behavior of impurities, and their respective electronic properties. PACS:Unfortunately, a direct experimental access to point defects in semiconductors is very difficult, because most experimental techniques rely on the interpretation of macroscopic data of differently processed crystals or on signals integrated over a large set of usually unknown defects. Conclusions about point defects on the atomic level were necessarily limited. In contrast, cross-sectional scanning tunneling microscopy (STM) allows us to directly image with atomic resolution individual point defects and dopant atoms. Crosssectional scanning tunneling microscopy is based on a simple concept: the defects inside the crystal are exposed by cleavage on a surface and subsequently imaged with atomic resolution using STM. Such images yielded a large variety of atomically resolved data about point defects and dopant * (Fax: +49-2461/61-6444, E-mail: p.ebert@fz-juelich.de) atoms. The results provided not only significant progress in the understanding of the fundamental physics of point defects in compound semiconductor surfaces, but it has even been possible to draw conclusions about properties of defects inside semiconductor crystals and the physics governing these bulk point defects [1].The present paper illustrates using selected examples of the progress we achieved in recent years in determining the physics governing the nano-scale properties of point defects in compound semiconductors and their surfaces. We concentrate, on the one hand, on anion surface vacancies as the purest example for surface defects in cleavage surfaces of III-V semiconductors and demonstrate the determination of the surface vacancies' key properties, such as chargetransition levels, electrical charge states, lattice relaxation, and interactions. On the other hand, it is shown how to extract the physics governing bulk point defects by STM. Particular focus will be on...

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Tunneling microscopy of point defects on GaAs(110)

Cited by 56 publications

References 0 publications

Breakdown of cation vacancies into anion vacancy-antisite complexes on III-V semiconductor surfaces

Breakdown of cation vacancies into anion vacancy-antisite complexes on III-V semiconductor surfaces

Three- to two-dimensional transition in electrostatic screening of point charges at semiconductor surfaces studied by scanning tunneling microscopy

Defects in III-V semiconductor surfaces

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