RU139673U1 - SEMICONDUCTOR NANOGETEROSTRUCTURE INALGAAS / INALAS / INAS METAMORPHIC BUFFER LAYER ON A GALLIUM ARSENIDE SUBSTRATE - Google Patents

Abstract

The proposed utility model relates to InAlAs / InGaAs / GaAs semiconductor nanoheterostructures with high electron mobility of the MNEMT type (metamorphic high electron mobility transistor) used for the manufacture of microwave transistors and monolithic integrated circuits of the millimeter wavelength range. The problem solved by this useful model is the creation of the so-called metamorphic nanoheterostructures of transistors with high electron mobility on GaAs substrates, the instrument characteristics of which would not be inferior to the characteristics of nanoheterostructures on InP substrates in the maximum mobility and electron concentration in the channel, and transistors based on them in maximum operating frequencies and minimum noise level. The technical result that allows us to accomplish the task is to suppress the penetration of dislocations into the active region of the transistor nanoheterostructure with high electron mobility and to suppress the development of the surface microrelief during the epitaxy process, which leads to a decrease in the surface roughness and heterogeneity of the nanoheterostructure, which reduces charge carrier scattering on the roughness and roughness helps to increase the mobility of charge carriers of a two-dimensional electron gas. The result is achieved through the use of a nanoheterostructure of a metamorphic buffer layer of a special original design, with a sharp stepwise change in the molar fraction of indium arsenide in the layers of solid solutions forming a nanoheterostructure, characterized in that the starting layer of a quaternary solid solution In _1-xy Al _y Ga _x As (5, Fig. 2), a stepwise increasing parameter of the crystal lattice immediately immediately after the formation of a buffer layer of gallium arsenide; three multilayer mechanically stressed superlattices In _1-xy Al _y Ga _x As / In _1-y Al _y As (7,9,11, Fig. 2), with different average molar fractions of indium arsenide and crystal lattice parameter, with a ratio of layer thicknesses quaternary and ternary solid solutions 2 to 1, 1 to 1 and 1 to 2, inhibiting the growth of misfit dislocations into the upper layers of the heterostructure and the development of the microrelief of the surface of the heterostructure; the final metamorphic layer of the In _1-y Al _y As ternary solid solution (13, FIG. 2), stepwise increasing the crystal lattice parameter to the desired final value; ultrathin InAs layers (6, 8, 10, 12, Fig. 2), placed at the beginning of each stepwise increase in the constant lattice of the heterostructure, ensuring the early formation of a network of misfit dislocations and their effective “healing” as the heterostructure is embossed.

Description

The utility model relates to semiconductor nanoheterostructures InAlAs / InGaAs / GaAs with high electron mobility type MNEMT (metamorphic high electron mobility transistor), used for the manufacture of microwave transistors and monolithic integrated circuits of the millimeter wavelength range.

In the field of frequency ranges from units to hundreds of gigahertz and power from milliwatts to hundreds of watts, a variety of semiconductor technologies and materials are used. The main types of transistors in this area are traditional field and bipolar devices, Schottky field effect transistors (MESFETs), heterojunction field effect transistors (NEMT, RNEMT, MNEMT), as well as heterojunction bipolar transistors (NVT).

Gallium arsenide is currently one of the main materials for the production of microwave devices. This is the first material mastered by the industry from the AZV5 semiconductor group, with which many prospects of microwave electronics are connected today. Against the background of this dominant technology today, areas are developing that may play a crucial role in microwave electronics tomorrow. First of all, we are talking about indium phosphide and solid solutions based on it [Y. Sato, T. Kita, S. Gozu, S. Yamada / Large spontaneous spin splitting in gate-controlled two-dimensional electron gases at normal http: //Ino.75Gao.25As/Ino.75Alo.25As heterojunctions // J. Appl . Phys., 89, 8017 (2001)]. The basic elements for the implementation of monolithic integrated circuits of the millimeter range at present are heterostructured field-effect transistors in the AlInAs / InGaAs material system grown on InP substrates, which significantly surpass the pseudomorphic AlGaAs / InGaAs NEMT transistors well mastered in production in maximum operating frequencies and minimum noise level.

Currently, MIS microwave based on AlInAs / InGaAs / InP HEMT transistors are quite widely produced and used in the USA, Japan and France. In particular, the creation of PNEMT with InGaAs / InAlAs / InP-structure on 100-mm wafers using 0.1-micron technology was one of the first to be announced by Northrop Grumman Space Technology (USA). This technology is the result of improving the manufacturing process already mastered by the company for manufacturing PNEMT on 75 mm plates, on the basis of which serial MISs are produced. In transistors created as part of this process,

the indium concentration in the InGaAs channel layer is 60%, the carrier mobility in the channel reaches 10,000 cm ² / V · s at an electron density in the channel of ~ 3.5 · 10 cm-2 [F. Capotondi, G. Biasiol, I. Vobornik, L. Sorba, F. Giazotto, A. Cavallini, B. Fraboni / Two-dimensional electron gas formation in undoped http: // InO.75 GaO.25As/ http: // InO. 75A10.25As quantum wells / J. Vac. Sci. Technol. B 22, 702 (2004)]. In this case, the transistor slope is approximately 800 mS / mm, the current density is 540 mA / mm, and the cutoff frequency is more than 190 GHz. On the basis of RNEMT with such a structure, the company created a number of MISs, in particular, a low-noise two-stage balanced Ka-band amplifier with a gain of more than 17 dB and a noise level of less than 2.4 dB in the range of 27-39 GHz.

The development of InGaAs / InAlAs / InP HEMT technology in Japan allowed Fujitsu Laboratories Ltd to demonstrate in June 2008 a prototype of a wireless data transmission system with a bandwidth of 10 Gbit / s, operating in the frequency range 70-100 GHz.

The advantage of heterostructures on InP substrates, in comparison with InGaAs / AlGaAs heterostructures grown on GaAs substrates, is the possibility to use layers with a higher indium content (a typical mole fraction of 0.5 in the case of an InP substrate, versus 0.2 in the case of a GaAs substrate). As a result, a larger gap in the conduction band at the channel / barrier heteroboundary, as well as a smaller effective mass of electrons in modulated doped heterostructures, which allows one to obtain a higher density (> 2 · 10 ¹² cm ^- 2) and greater mobility (> 10 000 cm ² / V · s) of electrons in a two-dimensional gas formed near the heterointerface.

However, InP substrates, in comparison with GaAs, have significant drawbacks: the smaller size of commercially available wafers, high fragility, and significantly higher cost. The high cost of the substrate significantly increases the cost of manufacturing transistor structures. The higher fragility of InP makes it difficult to manufacture devices based on them and reduces the yield of suitable devices due to the splitting of the plates during their processing. In this regard, the urgent task is to develop an alternative approach to heterostructures on indium phosphide - the creation of so-called metamorphic heterostructures on GaAs substrates (Fig. 1), the instrument characteristics of which would not be inferior to the characteristics of heterostructures on InP substrates.

A significant difference in the lattice constants of InP and GaAs (about 3.5%) makes it impossible to directly epitaxially grow perfect instrument structures on GaAs substrates, the lattice constant that would coincide with the lattice constant or even exceed the InP lattice constant, since in this case

the relaxation of emerging elastic stresses is accompanied by the formation of misfit dislocations that penetrate the entire thickness of the epitaxial layer and a sharp deterioration of all electrical parameters of the structure [S. Gozu, C. Tsuboki, M. Hayashi, C. L. Hong, S. Yamada // J. Cryst. Growth 201, 749 (1999); M. Matloubian et al., "Http://Gao.47bio.53 As / InP HEMTs with novel GaP _0.35 Sb _0.65 Schottky Layers Grown by MOVPE." Device Research Conference Charlottesville, Virginia, 32-33 (1998)]. The use of specific constructions and technological regimes for growing the transition layer allows us to switch from a GaAs constant lattice to an InP constant lattice [Naoki Nara, Naoya Okamoto, Kenji Imanishi, Tsuyoshi Takahashi, and Kozo Makiyama Imaging in Reliability of InP-Based HEMTs by Suppressing Impact Ionization Electronics and Communications in Japan , Part 2, Vol.90, No. 5th, 2007; K. Hetzer, WE Hoke, PJ Lemonias, JJ Mosca. / High indium metamorphic HEMT on a GaAs substrate / J. Vac. Sci. Technol. - 1999. - In 17 (3) 1131; M. Zaknoune, B. Bonte, C. Gaquiere. [Text] / IEEE Electron Device Lett. - 1998 .-- 9 (9), 345; Guanwu Wang, Youngkai Chen, William J.Scha. [Text] / IEEE Trans. Electron Devices. - 1988 .-- 35 (7), 818; M. Behet, K. Van der Zanden, G. Borghs. [Text] / http: //Appl.Phys.Lett. - 1998 .-- 73, 2760; T. Mishima, K. Higuchi, M. Mori. [Text] / J. Crystal Growth. - 1995. - 150]. The use of optimal deposition temperatures of the transition layer and other parameters of the epitaxial process allows one to “retain” most dislocations within the transition layer and prevent them from spreading to the layers of the transistor structure, to obtain smooth interfaces with a roughness of 1 nm at the damage, which reduces scattering on the roughness of the heteroboundary and contributes to increasing the mobility of charge carriers of a two-dimensional electron gas.

Typically, an AlInAs solid solution layer is used as the transition layer, the indium content of which, as a rule, varies linearly or stepwise from 10 to 52-60% [RF Patent RU 111352; RF patent RU 111353]. Under certain conditions, the network of dislocations does not propagate in the direction of growth and does not penetrate into the active layers of the structure, but “closes” inside this transition layer. Next, a transistor nanoheterostructure is grown on the surface of the transition metamorphic buffer layer. The basic design of a transistor heterostructure with high electron mobility on the surface of the transition metamorphic buffer layer, usually does not differ from the design of the transistor heterostructure grown directly on the surface of the InP substrate, if the crystal lattice parameter of the final part of the buffer layer is close to the crystal lattice parameter InP. On the other hand, the use of transient metamorphic buffer

layer allows you to go, in the final part of the buffer layer, to a parameter of the crystal lattice smaller or larger than the crystal lattice parameter InP. This opens up the possibility of using designs of transistor heterostructures with a large or lower molar fraction of InAs in the InGaAs channel layer and in the InAlAs barrier layer, depending on the tasks set. In other words, during epitaxy of transistor heterostructures on the surface of a metamorphic buffer, the requirement of mandatory lattice matching of all layers of the heterostructure with the crystal lattice parameter InP is removed, the required crystal lattice parameter in this case is set by a metamorphic buffer layer. Using identical growth rates of binary compounds during the epitaxy of InGaAs and InAlAs solid solutions in the final part of the buffer layer and in the transistor heterostructure allows automatic matching of the crystal lattice parameters.

The best mobility values for the AlInAs / InGaAs metamorphic transistor nanoheterostructures are 9900, 10000, and 12400 cm ² / Bxc at the indium concentrations in the InGaAs channel layer of 0.54, 0.56, and 0.60, respectively. In this case, the electron density in a two-dimensional gas can reach values> 3 · 10 ¹² cm ² .

However, the practical implementation of metamorphic GaAs heterostructures, transport and structural characteristics that would not be inferior to the characteristics of InP heterostructures, is hindered by incomplete suppression of the growth of dislocations in the active layers of the structure and the emergence of surface microrelief and requires careful optimization of the synthesis of such heterostructures by the molecular beam method epitaxy and their construction.

The problem solved by this useful model is the creation of metamorphic heterostructures with high electron mobility on GaAs substrates, whose instrumental characteristics would not be inferior to the characteristics of nanoheterostructures on InP substrates in the maximum values of electron mobility and electron concentration in the channel.

The technical result that allows us to fulfill the task is to reduce the density of dislocations in the active region of the nanoheterostructure and to reduce the roughness of the surface and heterointerfaces of the nanoheterostructure, which reduces the scattering of charge carriers on the roughness of the heterointerface and increases the mobility of charge carriers of a two-dimensional electron gas.

Technical result is achieved due to the fact that in the semiconductor nanogeterostruktur InAlGaAs / InAlAs / InAs metamorphic buffer layer on a substrate of gallium arsenide comprising a starter layer quaternary solid solution of In _1-xy Al _y Ga _x As, a layer of In _1-xy Al _y Ga _x As, three multilayer mechanically stressed superlattices In _1-xy Al _y Ga _x As / In _1-y Al _y As with different average molar fractions of indium arsenide and crystal lattice parameter and the final metamorphic layer of the ternary solid solution In _1-y Al _y As , three consecutively located superlattices alternating layers of In _1-xy Al _y Ga _x As / In _1-y Al _y As, in the ratio of the thicknesses of the layers of the quaternary and ternary solid solutions 2 to 1, 1 to 1 and 1 to 2, respectively, stepwise increase the crystal lattice parameter in the intermediate range from the start to the final layers of the heterostructure, and inhibit the growth of misfit dislocations in the upper layers of the heterostructure and the development of the microrelief of the surface of the heterostructure, and ultrathin InAs layers are placed at the beginning of each step increase in the lattice constant structures and provide early formation of a network of misfit dislocations and their effective “healing” as the heterostructure grows.

Figure 1 presents the basic cross-sectional diagram of a semiconductor metamorphic nanoheterostructure selected as a prototype of the claimed utility model. The following successive layers and their composition are indicated.

Figure 2 presents a detailed cross-sectional diagram of a nanoheterostructure of a metamorphic buffer layer of a special original design, demonstrating the essence of the claimed utility model. The following successive layers and their composition are indicated.

The semiconductor nanoheterostructure of the metamorphic buffer layer (3, Fig. 1) is grown by molecular beam or gas epitaxy after growing on the surface of gallium arsenide with a crystallographic orientation (100) a buffer epitaxial layer of gallium arsenide with a typical thickness of 150 ± 50 nm or more and consists of a starting layers of the In _1-xy Al _y Ga _x As quaternary solid solution, the InAs hyperfine layer, the In _1-xy Al _y Ga _x As layer, the InAs hyperfine layer, three mechanically stressed multilayer In _1-xy Al _y Ga _x As / In ₁ superlattices _-y Al _y As with various average mole nd fraction indium arsenide crystal lattice parameter and terminating metamorphic layer ternary solid solution of In _1-y Al _y As, a superlattice represent three alternating layers of In _{1-xy Al y Ga x As /} In _1-y Al _y As, in the ratio

the thicknesses of the layer of quaternary and ternary solid solutions 2 to 1, 1 to 1 and 1 to 2, respectively, stepwise increase the crystal lattice parameter in the intermediate range from the starting to the final layers of the heterostructure, inhibit the growth of misfit dislocations in the upper layers of the heterostructure and the development of the microrelief of the heterostructure surface, and ultrathin InAs layers are placed at the beginning of each stepwise increase in the lattice constant of the heterostructure, provide early formation of a network of dislocations of mismatch Corollary and effective "healing" as the cultivation of the heterostructure.

The equality of the molar fractions of the InAlAs, InGaAs ternary solid solutions ensures the lattice matching of the InAlAs, InGaAs ternary solid solutions and the final layer of the metamorphic buffer nanoheterostructure during subsequent growth of the transistor nanoheterostructure on it.

We denote the value of the InAs compound growth rate by the symbol A. The typical A values used for growing metamorphic transistor nanoheterostructures are in the range 0.1 ± 0.05 nm / s. The growth rates of AlAs and GaAs are chosen almost equal, we will designate them B. Typical values of B used for growing metamorphic transistor nanoheterostructures are also in the range 0.1 ± 0.05 nm / s. The molar fraction of Al, y, in the In _1-y Al _y As ternary solid solution is equal to the ratio B / (A + B), and the molar fraction of In, 1-y, is equal to the ratio A / (A + B). The molar fraction of Al, y, in the In _x1 Al _y Ga _1-x1-y As quadruple solid solution is equal to the ratio B / (A + 2B), the molar fraction of Ga, x, has the same value of B / (A + 2B), and the molar fraction of In, (1-x-y), is equal to the ratio A / (A + 2B). The ratio of the values of A and B is selected based on the task of further growing a transistor nanoheterostructure on a metamorphic buffer layer. The ratio A / (A + B) characteristic of metamorphic transistor nanoheterostructures varies in a rather wide range, 0.3–0.6. If, after the formation of a metamorphic layer nanoheterostructure on the surface of gallium arsenide, it is planned to grow a transistor heterostructure of a lattice matched with indium phosphide, then the A / (A + B) ratio is chosen equal to 0.520, then the nanoheterostructure consists of layers In _0.520 Al _0.480 As and In _0.352 Al _0.324 Ga _0.324 As.

The characteristic thicknesses of the layers of the nanoheterostructure of the metamorphic buffer layer (figure 2):

- the starting layer formed from a quaternary solid solution In _1-xy Al _y Ga _x As - 20 ± 5 nm (5, figure 2);

- the ultrathin layer of the InAs binary compound is 0.30 ± 0.03 nm (6, Fig. 2);

- a layer formed from a quaternary solid solution In _1-xy Al _y Ga _x As - 200 ± 10 nm (7, figure 2);

- an ultrathin layer of the InAs-binary compound 0.30 ± 0.03 nm (8, Fig. 2);

- intermediate layer No. 1, formed by the sequential growth of 10 or more pairs of alternating layers of In _1-xy Al _y Ga _x As / In _1-y Al _y As, the so-called superlattice No. 1, with a ratio of the thicknesses of the layer of quadruple and triple solid solutions 2 to 1, respectively, with characteristic layer thicknesses of 20 ± 1 nm and 10 ± 0.5 nm (9, FIG. 2);

- the ultrathin layer of the InAs binary compound is 0.30 ± 0.03 nm (10, Fig. 2);

- intermediate layer No. 2, formed by the sequential growth of 15 pairs or more alternating layers of In _1-xy Al _y Ga _x As / In _1-y Al _y As, the so-called superlattice No. 2, with a ratio of the thicknesses of the layer of quadruple and triple solid solutions 1 to 1, respectively, with characteristic layer thicknesses of 10 ± 0.5 nm (11, FIG. 2);

- the ultrathin layer of the InAs binary compound is 0.30 ± 0.03 nm (12, Fig. 2);

- intermediate layer No. 3, formed by the sequential growth of 10 pairs or more alternating layers of In _1-xy Al _y Ga _x As / In _1-y Al _y As, the so-called superlattice No. 3, with a ratio of the thicknesses of the layer of quadruple and triple solid solutions 1 to 2, respectively, with characteristic layer thicknesses of 10 ± 0.5 nm and 20 ± 1 nm (13, FIG. 2);

- the ultrathin layer of the InAs binary compound is 0.3 ± 0.03 nm (14, Fig. 2);

- the final layer formed from a ternary solid solution In _x1 Al _y As, with a characteristic thickness of 1000 nm or more (15, figure 2).

The lattice constant as the nanoheterostructure is grown increases stepwise and reaches its maximum value when growing the final layer.

The obtained InAlGaAs / InAlAs nanoheterostructure of the metamorphic buffer layer provides the possibility of further growing metamorphic nanoheterostructures of transistors with high electron mobility on GaAs substrates, the instrument characteristics of which are not inferior to the characteristics of nanoheterostructures on InP substrates in the maximum electron mobility and concentration in the channel, and transistors based on them maximum operating frequencies and minimum noise level.

Claims (1)

Semiconductor nanoheterostructures InAlGaAs / InAlAs / InAs metamorphic buffer layer on a substrate of gallium arsenide comprising a starter layer quaternary solid solution of In _1-xy Al _y Ga _x As, a layer of In _1-xy Al _y Ga _x As, three multilayer mechanically strained superlattice In _1-xy Al _y Ga _x As / In _1-y Al _y As with a different average molar fraction of indium arsenide and a crystal lattice parameter and a final metamorphic layer of a ternary solid solution In _1-y Al _y As, characterized in that there are three successive superlattices are alternating layers of In _{1- xy} Al _y Ga _x As / In _1-y Al _y As in the ratio of the thicknesses of the layers of the quaternary and ternary solid solutions 2 to 1, 1 to 1 and 1 to 2, respectively, stepwise increasing the crystal lattice parameter in the intermediate range from the starting to the final layers of the heterostructure inhibit the growth of misfit dislocations into the upper layers of the heterostructure and the development of the microrelief of the surface of the heterostructure, while the InAs ultrathin layers providing early formation of a network of misfit dislocations and their effective healing as the heterostrue grows structures are placed at the beginning of each stepwise increase in the lattice constant of the heterostructure.

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