The method of forming germanium nanoislands on vicinal silicon surfaces

 

Usage: in the field of nanoelectronics to create on the basis of structures nanostream (quantum dots) germanium on silicon semiconductor devices with ultra-high performance, as well as some of optoelectronic devices. The inventive method of forming germanium nanoislands on vicinal silicon surfaces is that the annealing vicinal si substrate at the stage precipitaciones training and during deposition Germany is produced by passing constant current in the direction perpendicular to the front steps of the vicinal faces of the silicon. The technical result of the invention is the formation of high-density highly organized and committed by the structure of the arrays of germanium nanoislands on vicinal silicon surfaces (III). 2 Il.

The invention relates to the field of nanoelectronics and can be used to create on the basis of structures nanostream (quantum dots) germanium on silicon semiconductor devices with ultra-high performance, as well as some of optoelectronic devices.

The most promising method of forming structures with nanotron the effect of self-organization of surface in heteroepitaxial systems due to the relaxation of elastic stresses, due to the mismatch of the parameters of crystal lattices of the film and substrate. For the system silicon-germanium samoformiruyushchikhsya the germanium nanoislands are characterized by relatively large lateral dimensions, which does not allow to fully manifest the effects of size quantization in such structures. In addition, localization of Islands in the plane of the heterojunction has a random character. Reducing the size of the Islands is generally achieved through the use of low temperatures of the substrate during deposition of the film Germany, which degrades the crystalline perfection of self-organizing nanostruc and increases their heterogeneity in size. Examples of the effect of DC to influence the size and the degree of ordering of nanostruc in the system silicon-germanium is unknown to us.

In the formation of structures with germanium nanoislands on silicon is typically used following sequence of technological operations (see, for example, N. In. Vostokov, S. A. Gusev, I. C. Debts etc./FTP, T. 34, vol. 1, S. 8-12 (2000); O. P. Pchelyakov, Y. B. Bolkhovityanov, A. C. dvurechensky and other TEKHN, T. 34, vol.11, S. 1281-1299 (2000)): 1) to create an atomically clean surface Albom the flux of atoms of silicon in ultrahigh vacuum conditions; 2) is grown buffer layer of silicon of a thickness of 20-200 nm; 3) next, the substrate with the indirect source is heated to a certain temperature (usually 200-700oC), which will be deposited film Germany; 4) deposition of the film Germany effective thickness of from 3 to 15 monoatomic layers (1 ML =0.14 nm) at a rate of film growth is from 0.01 to 0.05 nm/s; 5) in some cases is more (pokerstove) annealing of the crystals after the deposition of Germany at the temperature of the substrate 500-700oFrom within 3-30 minutes

Formed through the self-organization of the surface of the germanium nanoislands have the following major drawbacks: 1) at relatively high temperatures of the substrate during deposition Germany (500-700oC) samoformiruyushchikhsya Islands are characterized by large lateral dimensions (150-300 nm), significantly greater than the wavelength of de Broglie for this system that does not allow you to manifest the effects of size quantization in data structures; 2) reduce the size of the Islands can be achieved through the use of low temperatures of the substrate during deposition of the film Germany (200-300oC). However, the nature of the surface morphology is determined by kineticenergy islets in size; 3) and in the first and in the second case, the localization of the Islands in the plane of the interface film-substrate has a random character.

The present invention is the formation of high-density, highly organized and committed by the structure of the arrays of germanium nanoislands on a vicinal surface of si (111).

This object is achieved due to the fact that the heating vicinal si substrate is produced by passing constant current in the direction perpendicular to the front steps of the vicinal faces of silicon.

In Fig. 1 shows the AFM image of the topography of the structure with germanium nanoislands on the surface of the silicon (111) formed in the following manner: a silicon substrate mark KES - 0.01 (111), which is a rectangular strip of 0.3415 mm, with double misorientation from the original plane was placed in a vacuum chamber. After reaching the working vacuum cleaned surface of the silicon layer from the natural oxides and inclusions of silicon carbide two-minute annealing of crystal direct transmission of direct current in the direction of the lower terraces (Fig.2) at a temperature of 1250oher but, on the contrary, the surface roughness was smoothed out. Further, the direction of the current was reversed and it was a 30-second annealing the crystal at a temperature of 1220oWith the aim of forming a stepped structure of the substrate. Then, by reducing the density passed through the sample DC (reducing the intensity of the electric field E is applied to the sample), the temperature of the substrate was lowered to 500oWith and produced coating film Germany with an effective thickness of close to 6 ML (0,9 nm) at a growth rate of 0.05 nm/s with further pokerstove annealing DC for 10 minutes. As a result, the surface of the formed system of highly ordered germanium nanoislands, built strictly along the front of nanostore substrate. The dimensions of the base of the Islands does not exceed 30 nm, the density of the islets close to 11011cm-2.

The effect of ordering nanostruc is due to the fact that: 1) the deposition of Germany is on the shaped substrate, on which nanostore formed as a result of annealing of the crystal by passing constant current in the direction perpendicular FR is a major deviation from the original plane, annealing which leads to the formation of the steps with a sawtooth geometry of the front. Sawtooth edges formed steps in the future are centres of fixing adatoms Germany, forming nanostruc;
3) to enhance the directional flow of adatoms on the stages of the deposition film and pokerstove annealing is used, the effect of direct current (electromigration), builds nanostruc besieged Germany along the front of nanostore substrate.

The use of the proposed method of forming germanium nanoislands on vicinal silicon surfaces provides in comparison with existing methods the following benefits:
1) makes it possible to obtain spatially ordered arrays of nanostruc high density;
2) allows to obtain the small islets at a relatively high temperature of the substrate (500oC), which reduces the likelihood of defects in the crystal structure in such objects.


Claims

The method of forming germanium nanoislands on vicinal silicon surfaces, which consists in annealing in vacuum silicon substrate (III) with a double misorientation from iact by passing a constant current perpendicular to the front steps of the vicinal faces of silicon in the direction providing the unevenness of the surface, subsequent annealing the silicon substrate at the change of current direction on the opposite for forming a stepped structure, temperature reduction, spraying, Germany, followed pokerstove annealing DC.

 

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