RU2091911C1 - High-frequency gunn-effect device - Google Patents

Abstract

FIELD: radio equipment for generating microwaves. SUBSTANCE: current-injecting cathode region of device uses Gunn effect and is made in the form of local heteroinjectors built of material whose forbidden gap is smaller than that of material n-GaAs,AL_xGa_1-xAs with constant value of x parameter contacting on one side n-GaAs material and forming with the latter abrupt heterojunction; on other side, it contacts Al_xGa_1-xAs layer with parameter x descending to zero towards n⁺⁺-GaAs layer on cathode contact side; layer whose parameter xAl_xGa_1-xAs linearly varies and which is placed between material Al_xGa_1-xAs having constant x parameter of same value as that of the former on contacting barrier and n⁺⁺-GaAs layer. Heteroinjector is surrounded with region limiting current injection which is made in the form of Schottky barrier. Parameter x is found from condition 0<x≅0,23 and energy ε accumulated by carriers on heteroinjector length meets condition ε ≅ Δ_γL, where Δ_γL is energy gap between GaAs valleys γ and L. Carrier concentration in n⁺-layer satisfies condition n<n⁺<n⁺⁺, where n⁺⁺ and n concentrations are chosen from conditions 8·10¹⁷≅n≅5·10¹⁸,cm^-3, 3·10¹⁵≅n≅1,4·10¹⁶,cm^-3. Local heteroinjectors are made in the form of cylindrical regions directed inside semiconductor material; cylinder bases are located in device cathode contact plane and their generating line is perpendicular to cathode contact plane. EFFECT: improved design. 4 cl, 10 dwg

Description

 The invention relates to electronic equipment, namely to a semiconductor device based on electron transfer and can be used in electronic equipment to generate microwave oscillations.

Existing devices based on the Gunn effect (Gunn diodes) do not allow efficient operation in the submillimeter wavelength range, since the designs of such devices limit the frequency range and efficiency due to the large initial heating zone of the carriers ("dead" zone). The "dead" or "cold" zone is usually called the region adjacent to the cathode of the device, in which the electrons acquire energy equal to the energy gap between the G and L valleys of the semiconductor material Δ _GL (see Reviews on electronic technology, ser. 1: Microwave electronics, vol. 4 (1008), Kalfa A.A. Poresh SB, Tager A.S. Gann effect at high frequencies, 1984 p. 16) [1]
Further advancement into the submillimeter frequency range can be carried out while providing additional heating of the carriers in the application area of devices such as Gunn diodes.

An attempt to provide additional heating of carriers in the cathode region was made in the device described in the article (see MRFriscourt, PA Rolland and M.Pernisek "Heterojunction Cathode Contact Transferred-Electron Oscillators", IEEE Electron Device Letters, vol. EDL-6, N 10 , October 1985, pp. 497-499). [2]
A semiconductor device based on electron transfer consists of the -n ⁺ : Ga Al As cathode, the n: GaAs active region of the device and the n ⁺ anode, i.e., n ⁺ : Ga Al As / n: GaAs / n ⁺ structures. As the cathode material of the device, a wider-band Ga Al As material is used, in comparison with the material in the active region of the GaAs device. As indicated in this paper (p. 498), the idea of using such a cathode is related to the fact that in this case, hot electrons with an energy slightly smaller than the intervalley energy gap Δ are injected from the cathode (Ga Al As) into the active region of the device (n GaAs) _{GL of the} GaAs semiconductor material, which makes it possible to exclude the passive “dead” zone from the interaction site and substantially resolve the frequency range of the device.

The disadvantage of such a device, as indicated in the same work (p. 498), is the absence of a sufficient pulling field in the semiconductor material from the n GaAs side adjacent to the cathode of the device (Ga Al As) in the considered n ⁺ Ga Al As / n GaAs heterojunction, which generates a rather significant area of the virtual cathode of the device. As a result, the dead zone of such a device only decreases slightly, and the frequency range of the diode under consideration, as indicated in the same work (p. 498), does not actually change compared to the usual n ⁺ -nn ⁺ GaAs Gunn diode.

Known semiconductor device on the Gunn effect, selected as a prototype (see UK patent N 1514240, published June 14, 1978. the applicant company "THOMSON-CSF", France, CL H 01 L 47/02). [3]
The Gunn effect semiconductor device contains active layers made of GaAs semiconductor material of this type of conductivity, a first anode contact and a second cathode contact containing a plurality of first zones capable of injecting current into the device and a plurality of second zones forming rectifying contacts with the active zone, the first and the second zone is located on the surface of the active layer opposite the anode contact, forming a mosaic. The device also contains a metal electrode located in the first and second zones. In the device, the first zones are also formed using a metal alloy, the second zones are formed from a second metal alloy and are brought into contact with the active layer, forming the Schottky barrier (BS) with the latter.

In the description of the device according to the prototype, it is indicated that the limited current injection in the diode implemented using the island structure of the cathode guarantees the existence of a nonzero pulling field in the immediate vicinity of the cathode and a more uniform field distribution along the entire length of the diode. Moreover, the current distribution in this diode is no longer unidirectional, like n ⁺ -nn ⁺ diode (analog), but three-dimensional. The dimensions and density of the regions (the number of regions per unit area of the cathode) injecting current in the cathode region of the specified diode (prototype design) determine the density of the injection current.

 The presence of a nonzero pulling field in the immediate vicinity of the cathode makes it possible to reduce the initial carrier heating zone (“dead” zone) and to expand the frequency range of the device compared to the design of the analog device.

Nevertheless, it (the "dead" zone) remains, since the electrons need to gain energy ε satisfying the condition e ≅ Δ _GL , where Δ _{GL is the} energy gap between the central and nearest side valleys of the semiconductor material. Moreover, the situation is worsened by the fact that the field decreases deep into the semiconductor material of this device. Thus, the prototype Gunn-based semiconductor device has one of the following disadvantages: injection of “cold” carriers into the active region of the device, and, as a result, the presence of a “dead” zone that degrades the frequency characteristics of the device.

 The basis of the invention is the task of creating such a high-frequency Gunn device, in which a new implementation of the cathode of the device is carried out, containing from the areas injecting current into the device and limiting the current injection, and many of the areas injecting current into the device are made of semiconductor material with a larger band gap than semiconductor material n type conductivity. This allows due to the heating of the carriers in the cathode region to reduce the "dead" zone of the inventive device and, as a result, expand the frequency range of this device.

Gunn-effect high-frequency device containing n-type GaAs semiconductor material, n ⁺⁺ - GaAs semiconductor layers formed on it from the anode contact side and local n ⁺⁺ -GaAs conductivity layers in the cathode contact regions injecting current, anode contact and a cathode contact comprising a first plurality of current injection regions in devices and a second plurality of regions restricting current injection into the device, wherein the current injection regions into the device form a planar array To the invention of the cathode region, the current injecting currents into the device are made in the form of local heteroinjectors sequentially consisting of a semiconductor material with a larger band gap than n GaAs, Al _x Ga _1-x As material with a constant value of the parameter x, which contacts the semiconductor on one side material n GaAs and forming a heterojunction with it, on the other hand, is in contact with the Al _x Ga _1-x As layer with a linearly decreasing parameter x to zero in the direction to the n ⁺⁺ GaAs-type conductivity layer on the cathode contact side, at the layers with a linearly varying parameter x Al _x Ga _1-x As are between the material Al _x Ga _1-x As with a constant parameter x and have the same parameter x at the contact boundary, and an n ⁺⁺ type conductivity layer, moreover, the hetero injector is surrounded by a region restricting the injection of current, made in the form of a reverse-biased Schottky barrier, and the parameter x is selected from the condition 0 <x ≅ 0.23, and the energy ε accumulated by the carrier along the length of the hetero injector satisfies the following relation e ≅ Δ _GL , where Δ _{GL is the} energy the gap between G and L valleys of GaAs.

In addition, in a high-frequency device based on the Gunn effect, the carrier concentration in the n ⁺ -type layer satisfies the following relation:
n ⁺⁺ > n ⁺ > n,
where the concentration of carriers n ⁺⁺ , n is selected from the following conditions:
8 • 10 ¹⁷ ≅n≅5 • 10 ¹⁸ , cm ^-3
3 • 10 ¹⁵ ≅n≅1.4 • 10 ¹⁶ , cm ^-3 .

Кроме того, в высокочастотном приборе на эффекте Ганна локальные гетероинжекторы выполнены в виде цилиндрических областей направленных вглубь полупроводникового материала, причем основания цилиндров лежат в плоскости катодного контакта прибора, а их образующая перпендикулярна плоскости катодного контакта.In addition, in a Gunn-effect high-frequency device, the sum l _{Σ of the} length of the region with a ramp value of the parameter x Al _x Ga _1-x As and the length of the region with a constant value of the parameter x Al _x Ga _1-x As satisfy the following relation

In addition, in a high-frequency device based on the Gunn effect, local heteroinjectors are made in the form of cylindrical regions directed in-depth to the semiconductor material, with the bases of the cylinders lying in the plane of the cathode contact of the device, and their generatrix perpendicular to the plane of the cathode contact.

ячейки прибора, представленной на фиг. 4, катод который смещен на величину -

внешнего напряжения, приложенного к данному прибору; на фиг. 6 - зависимость распределения поля по длине прибора под гетероинжектором через четверть периода

; кривые 1, 2, 3 и 4, соответственно; на фиг. 7 - зависимость распределения концентрации свободных носителей по длине прибора под гетероинжектором через четверть периода

, кривые 1, 2, 3 и 4, соответственно; на фиг. 8 зависимость распределения поля по длине прибора под областью, ограничивающей инжекцию тока при выборе точки отсчета начиная от гетероперехода n⁺ Al_xGa_1-xAs/n GaAs через четверть периода

, кривые 1, 2, 3 и 4, соответственно; на фиг. 9 зависимость концентрации свободных носителей по длине прибора под областью, ограничивающей инжекцию тока при выборе точки отсчета начиная от гетероперехода n⁺ -Al_xGa_1-x As/n GaAs через четверть периода

, кривые 1, 2, 3 и 4, соответственно; на фиг. 10 зависимость эффективности n высокочастотного прибора на эффекте Ганна с гетероинжектором (кривая 1) и высокочастотного диода с "островковым" контактом (кривая 2) от частоты f.In FIG. 1 shows a general view of a high-frequency device based on the Gunn effect; in FIG. 2 the same, section AA of a high-frequency device based on the Gunn effect; in FIG. 3 part of the AA section (cell) of a high-frequency device based on the Gunn effect; in FIG. 4 cell of the periodic structure of a high-frequency device based on the Gunn effect; FIG. 5 profile of the conduction band along the cross section

cell of the device shown in FIG. 4, the cathode which is offset by -

external voltage applied to this device; in FIG. 6 - dependence of the field distribution along the length of the device under the hetero injector after a quarter of a period

; curves 1, 2, 3, and 4, respectively; in FIG. 7 - dependence of the distribution of the concentration of free carriers along the length of the device under the hetero injector after a quarter of a period

, curves 1, 2, 3 and 4, respectively; in FIG. Figure 8 shows the dependence of the field distribution along the length of the device under the region restricting the current injection when choosing a reference point starting from the n ⁺ Al _x Ga _1-x As / n GaAs heterojunction after a quarter of a period

, curves 1, 2, 3 and 4, respectively; in FIG. Figure 9 shows the dependence of the concentration of free carriers along the length of the device under the region restricting the current injection when choosing a reference point starting from the n ⁺ -Al _x Ga _1-x As / n GaAs heterojunction after a quarter of a period

, curves 1, 2, 3 and 4, respectively; in FIG. 10 shows the dependence of the efficiency n of a high-frequency Gunn effect device with a hetero injector (curve 1) and a high-frequency diode with an island contact (curve 2) on the frequency f.

To expand the frequency range of a high-frequency device based on the Gunn effect, it is necessary to reduce the "dead" zone of this device. Reducing the "dead" zone of the device under consideration can be achieved by heating the media in a special cathode region of the inventive device, called a hetero-injector. In the inventive high-frequency device based on the Gunn effect with an island heteroinjector (DOCG), electrons are injected from the heteroinjector into the active region (n-GaAs) of this device with an energy ε satisfying the condition e ≅ Δ _GL , while in the prototype device they are injected into the active region of the device with an energy of approximately CT (where K is the Boltzmann constant).

Consider in more detail the heating of the media in the injector of the inventive device (see Fig. 4), where
1) ABWS is the n ⁺⁺ GaAs region directly below the AB region, which injects current into the device and is an ohmic contact;
2) SWPK is the n ⁺ Al _x Ga _1-x As region, where x varies linearly from zero to 0.23 (0 <x≅0.23) along the device in the WP direction;
3) KPNM is the n ⁺ Al _x Ga _1-x As region;
4) BCDGMNPWB is the n-GaAs region of the device under consideration, including the active region of this device and located under the BC region, which limits the current in the device;
5) GDEF is the n ⁺⁺ GaAs region of the anode of the device.

, (см. фиг. 5), катод которого смещен на величину

внешнего напряжения, приложенного к прибору. Носители, инжектируемые в прибор через область AB, имеют наиболее вероятную энергию приблизительно KT. Учитывая тот факт, что область AB (фиг. 4) имеет островковый характер, нормальное поле E_вх на входе данной области, как и у прибора по прототипу, будет удовлетворять неравенству E_вх≥E_a, где E_a нормальное поле у FE области омического контакта анода. Под действием данного поля на толщине l₁ n⁺⁺- GaAs области инжектируемые электроны приобретают энергию V₁, которая увеличивает вероятность преодоления потенциального барьера V₂. Заметный наклон зоны проводимости

(фиг. 5) в области омического контакта AB (см. фиг. 4) обусловлен значительной величиной поля E_вх, то есть данный омический контакт работает в отличие от омического контакта EF не в омическом режиме. Потенциальный барьер V₂ образован при контакте n⁺⁺ GaAs и n⁺ Al_xGa_1-xAs областей, причем n⁺ Al_xGa_1-xAs область имеет следующую зависимость параметра x: на участке WP, длина которого l₂, параметр x изменяется линейно от нуля до 0.23, на участке l₃ параметр x 0.23.Note that the region of the hetero injector of a high-frequency device based on the Gunn effect represents the sum of the regions described in paragraphs 1, 2, and 3. It seems most convenient to consider the heating of electrons in the heterojector of the claimed device through analysis of the profile of the conduction band of this device along the section

, (see Fig. 5), the cathode of which is offset by

external voltage applied to the device. Carriers injected into the device through region AB have the most probable energy of approximately KT. Considering the fact that the region AB (Fig. 4) is insular in nature, the normal field E _in at the input of this region, like the prototype device, will satisfy the inequality E _in ≥ E _a , where E _{a is the} normal field in FE of the ohmic region contact anode. Under the influence of this field on the thickness l ₁ n ⁺⁺ - GaAs region, the injected electrons acquire energy V ₁ , which increases the probability of overcoming the potential barrier V ₂ . Marked slope of the conduction band

(Fig. 5) in the region of the ohmic contact AB (see Fig. 4) is due to a significant field E _input , that is, this ohmic contact does not work in contrast to the ohmic contact EF in the ohmic mode. The potential barrier V _{2 is} formed upon the contact of the n ⁺⁺ GaAs and n ⁺ Al _x Ga _1-x As regions, and the n ⁺ Al _x Ga _1-x As region has the following dependence of the parameter x: on the WP segment, whose length is l ₂ , the parameter x varies linearly from zero to 0.23; in the region l _{3, the} parameter x 0.23.

(см. фиг. 5) характеризуется встроенным полем, которое является следствием изменения параметра x в Al_xGa_1-xAs и которые в совокупности с полем E_вх и внешним полем позволяет значительной части носителей (электронов) преодолеть потенциальный барьер V₂. Носители, преодолевшие барьер V₂, попадают в область

(фиг. 5). Поле в

области образуется совместным влиянием внешнего поля и поля, образованного в областях

. Характер наклона зоны проводимости в этой области указывает на то, что носители, прошедшие данную область имеют энергию отсчитанную относительно края рассматриваемого участка зоны проводимости больше или равное, чем V₃= q•E $\genfrac{}{}{0ex}{}{\text{ср}}{\text{3}}$ •l₃,
где E $\genfrac{}{}{0ex}{}{\text{ср}}{\text{3}}$ среднее поле в CD области (фиг. 5). в/м;
l₃ толщина PN области (фиг. 4), м;
g заряд электрона, K.Region

(see Fig. 5) is characterized by an integrated field, which is a consequence of a change in the parameter x in Al _x Ga _1-x As and which, together with the field E _in and the external field, allows a significant part of the carriers (electrons) to overcome the potential barrier V ₂ . Carriers that overcome the V ₂ barrier fall into the region

(Fig. 5). Field in

areas formed by the combined influence of an external field and a field formed in areas

. The nature of the slope of the conduction band in this region indicates that carriers passing through this region have an energy counted relative to the edge of the considered section of the conduction band greater than or equal to V ₃ = q • E $\genfrac{}{}{0ex}{}{\text{wed}}{\text{3}}$ • l ₃ ,
where e $\genfrac{}{}{0ex}{}{\text{wed}}{\text{3}}$ average field in the CD region (Fig. 5). in / m;
l ₃ thickness of the PN region (Fig. 4), m;
g is the electron charge, K.

Carriers emerging from the hetero injector and entering the active region of the device through MN (Fig. 4), in addition to energy V _3, also have an energy V ₄ equal to ΔE _c discontinuous conduction bands between Al _x Ga _1-x As and GaAs to the right of the injector (Fig. . 4), and the physico-topological parameters of the injector of the inventive device are selected so as to satisfy the following inequality:
V ₃ + V ₄ ≅ ε ≅ Δ _GL , where (1)
Δ _GL energy gap between G and L valleys of GaAs.

, к данной области приложено напряжение V₅/g, где V₅ энергетический зазор, на который сдвигаются концы зоны проводимости активной области заявляемого прибора при приложении к нему внешнего напряжения

, gv; g заряда электрона, K.According to FIG. 5, for the passage of carriers through the active region of the claimed device

, voltage V ₅ / g is applied to this region, where V _{5 is the} energy gap, by which the ends of the conduction band of the active region of the inventive device are shifted when an external voltage is applied to it

, gv; g of the electron charge, K.

(фиг. 5) поле незначительно и поэтому участок зоны проводимости FH данного прибора является практически горизонтальным. В качестве области катода, ограничивающей инжекцию тока в заявляемый прибор, выбран барьер Шоттки BC (фиг. 4), причем величина барьера Шоттки выбирается такой, чтобы ток через указанный барьер не проходил. С другой стороны величина внешнего напряжения

, приложенного к БШ (барьер Шоттки) области, приводит к существованию ОПЗ (области пространственного заряда) под областью BC (фиг. 4), которые исключают протекание тока через BWPN область гетероинжектора (см. фиг. 4), а только через MN. Итак, в заявляемом высокочастотном приборе на эффекте Ганна носители впрыскиваются из инжектора в активную область прибора с энергией ε, удовлетворяющей условию e ≅ Δ_ГL.We believe that in the region of the anode

(Fig. 5) the field is insignificant and therefore the portion of the conduction band FH of this device is almost horizontal. As the cathode region restricting the injection of current into the inventive device, the Schottky barrier BC is selected (Fig. 4), the Schottky barrier being selected so that the current does not pass through the said barrier. On the other hand, the magnitude of the external voltage

applied to the BS (Schottky barrier) region leads to the existence of an SCR (space charge region) under the BC region (Fig. 4), which exclude the flow of current through the BWPN region of the hetero injector (see Fig. 4), but only through MN. So, in the inventive high-frequency device based on the Gunn effect, carriers are injected from the injector into the active region of the device with an energy ε satisfying the condition e ≅ Δ _GL .

On the other hand, to expand the frequency range of the claimed device, it is necessary not only the injection of "hot" electrons in the active region of the device, but also the presence of a nonzero normal field E _ov in the region MN (Fig. 4), satisfying the condition E _o > E _a . This condition is necessary to reduce the virtual cathode in the MN region (Fig. 4), which, as shown in the work (see (C. Moglestue // "Physica", 1985, BC. 129, N 1-3, pp. (552 -556)), p. 553) increases its volume at low fields E _o . In this work, it was shown that only approximately 25% of the carriers do not return to the heterojunction at given normal fields in the interface region of this heterojunction.

Another necessary characteristic of the carriers injected from the injector into the active region of the claimed device is their concentration, the value of which is proportional to the increase in the efficiency of this device and, consequently, the increase in the frequency range of the device under consideration. As a result, a detailed examination of the injection of carriers into the active region of a high-frequency device based on the Gunn effect in order to expand its frequency range puts forward the following requirements for the carriers injected into the device:
1) the energy of these carriers ε must satisfy the inequality; e ≅ Δ _GL
2) the field in the boundary region of the section "heteroinjector active region" must satisfy the condition E _o > E _a ;
3) the concentration of injected media in the active region of the inventive device should be optimal in terms of efficiency and, accordingly, the expansion of the frequency range of this device.

, достаточна для предотвращения туннелирования носителей из n⁺⁺- GaAs области омического контакта в активную n область заявляемого прибора. Указанную толщину Al_xGa_1-xAs слоя нежелательно увеличивать, так как будут расти суммарные потери в данном приборе.Consider the design requirements of the heteroinjector from the point of view of the requirements for the design of the heteroinjector from the point of view of the requirements of paragraphs 1), 2) and 3). According to the work (see book Zi S. M. Physics of Semiconductor Devices, vol. 2, M. Mir, 1984, p. 102) based on the formula for tunneling carriers through a barrier in the WKB (Wenzel Krames Brillouin method), the numerical approximation was obtained that the thickness of the Al _x Ga _1-x As layer in the hetero injector of the inventive device (between the n ⁺⁺ region of the ohmic contact and the active n region) is approximately (1500 1700)

is sufficient to prevent tunneling of carriers from the n ⁺⁺ - GaAs region of the ohmic contact into the active n region of the claimed device. The indicated thickness of the Al _x Ga _1-x As layer is undesirable to increase, since the total losses in this device will increase.

с линейным изменением параметра x от нуля до 0,23 в направлении от рассматриваемой границы раздела. Необходимость в существовании рассматриваемой области возникает также с точки зрения реализации омического контакта в области катода высокочастотного прибора на эффекте Ганна с островковым гетероинжектором. Дело в том, что практическая реализация омического контакта к GaAs гораздо проще, чем к Al_xGa_1-xAs.In (WG Oldham, AG Milnes, Solid-St. Electron. Vol. 6, 121 (1963)), it was found that the decrease in the conductivity band gap ΔE _c in the n ⁺ Al _x Ga _1-x As / n GaAs heterojunction between n ⁺⁺ GaAs by the region of ohmic contact and the n ⁺ Al _x Ga _1-x As layer is realized if the transition region from one material to another is smooth rather than sharp. According to the works (see DT Cheung, SY Ghiang, GL Peason, Solid-St. Electron. Vol. 18, p. 263 (1975)) and see (SR Weinzierl, JP Krusius, IEEE Trans. On Eiectron Devices, vol. 39, No. 5, 1992, p. 1050), and also based on numerical calculations, it was found that to neglect the reflection coefficient of the carrier during the transition of the latter from n ⁺⁺ GaAs to the n ⁺ Al _x Ga _1-x As region, we need an Al _x layer Ga _1-x As at least 500 thick

with a linear change in the parameter x from zero to 0.23 in the direction from the considered interface. The need for the existence of the region under consideration also arises from the point of view of realizing ohmic contact in the cathode region of a high-frequency device based on the Gunn effect with an island heteroinjector. The fact is that the practical implementation of ohmic contact with GaAs is much simpler than with Al _x Ga _1-x As.

As a material with a wide band gap than GaAs, Al _x Ga _1-x As was taken, which forms the basis of the hetero-injector of the carriers of the claimed device. The energy gap between the n ⁺ - Al _x Ga _1-x As region of the injector and the n GaAs region of the active region of the inventive device, forming a sharp heterojunction, is determined according to the empirical relation:
ΔE _c = 0.7 • [E _g Al _x Ga _1-x As-E _g GaAs]
in accordance with (TW Hickmott, et all, J. Appl. Phys. 57, 2844 (1985)), (MO Watanabe, et all, J. Appl. Phys. 57, 5340 (1985)), and the parameters x satisfy the following inequality:
0 <x ≅0.23
For x> 0.23, the depth of the donor levels in Al _x Ga _1-x As increases sharply (see book Peka G.P. Kovalenko V.F. Smolyar A.N. Varizon semiconductors, Kiev, Vyshcha Shkola, 1989) S. 34, Fig. 1.10), which leads to freezing of the carriers in the heteroinjector at nitrogen temperatures, overlapping levels of impurities of various valleys in the conduction band Al _x Ga _1-x As. For x> 0.23, the probability of carrier transition from Г to L valley to Al _x Ga _1-x As also significantly increases, which is undesirable.

, где z координата вдоль прибора. В итоге нормальное поле E_вых на границе раздела n⁺ - Al_xGa_1-xAs/n GaAs будет обеспечиваться только за счет увеличения нормального поля "островковой" области катода E_вх на выходе гетероинжектора заявляемого прибора за счет уменьшения площади сечения области, инжектирующей ток в данный прибор. Улучшить ситуацию путем повышения внешнего напряжения

эффективно не удается.The case of small x. In the case of small x, it has the initial nonoptimality of the device, which consists in the fact that the influence of the built-in field in the region of the hetero injector is lost, since with a decrease in the parameter x decreases ΔE _c (gap of the conduction band between n ⁺ - Al _x Ga _1-x As / n GaAs areas) and

where z is the coordinate along the device. As a result, the normal field E _o at the n ⁺ - Al _x Ga _1-x As / n GaAs interface will be provided only by increasing the normal field of the "island" region of the cathode E _in at the output of the hetero injector of the inventive device by reducing the cross-sectional area of the injecting region current to this device. Improve the situation by increasing external stress

effectively fails.

The concentration of carriers in the n ⁺ region of the Al _x Ga _1-x As layer (WSKMNPW, Fig. 4) satisfies the following relation:
n ⁺⁺ > n ⁺ > n,
where n is the concentration of carriers in the active region of the claimed device;
n ⁺⁺ carrier concentration under the cathode region injecting current into the device.

Note that n ⁺⁺ and n are within the following limits:
8 • 10 ^{17 ++} n ⁺⁺ ≅5 • 10 ¹⁸ , cm ^-3
3 • 10 ^{15 ++} n ⁺⁺ ≅1.4 • 10 ¹⁶ , cm ^-3
The lower limit of n ⁺⁺ carriers below the cathode region injecting current into the device is determined by the existence of good ohmic contact to the n ⁺⁺ region of the cathode. The upper limit of n ⁺⁺ concentration is determined by the dissolution limit of the dopant in this material (GaAs).

 The upper and lower limits for the carrier concentration n in the n-type semiconductor material are determined by the region of existence of the Gunn effect for this type of semiconductor material (n GaAs). As numerical calculations show, for a carrier concentration n in a semiconductor material outside these boundaries, the Gunn effect for this type of semiconductor material is unstable.

где z координата вдоль прибора);
в) выбор величины n⁺ позволяет оптимальным образом подбирать величину тока инжекции в активную область высокочастотного прибора на эффекте Ганна с точки зрения эффективности данного прибора.Inequality (2) is necessary to ensure conditions 1) 3) for carriers injected into the active region of the device, namely;
a) in order to obtain a given value ΔE _c (gap of the conduction band between n ⁺ -Al _x Ga _1-x As / n GaAs regions), which ultimately contributes to the condition ε ε Δ _ГL
b) taking into account the fact that an increase in the concentration of donor impurity in n ⁺ -Al _x Ga _1-x As reduces the average field in the region of the heteroinjector, it can thus control this field in order to ensure the condition E _o ≥ E _a (increase in the concentration of donor impurity in n ⁺ Al _x Ga _1-x As regions to decrease

where z is the coordinate along the device);
c) the choice of n ⁺ allows you to optimally select the value of the injection current into the active region of a high-frequency device based on the Gunn effect from the point of view of the efficiency of this device.

The hetero-injector of a high-frequency device based on the Gunn effect is made in the form of cylindrical structures located directly under the cathode electrode along the device in a volume of n GaAs. This embodiment of heteroinjectors provides the following advantages:
a) in the active region of the claimed heteroinjector immediately behind the islet heteroinjector, the increased field value of this heteroinjector decreases, since the carriers injected in the active region of the device in question can generally move in any direction of the positive hemisphere. This embodiment of the hetero injector allows this hetero injector not to impose its field in the active region of the device, i.e. there is no need to create a thin highly doped n ⁺⁺ GaAs region immediately behind the hetero injector (in the active region) to exclude the influence of the hetero injector field on the active region of the device, although at the heterointerface n ⁺ - Al _x Ga _1-x As / n GaAs normal field is significant in order to reduce the virtual cathode in this area;
b) the cylindrical execution of the injection region and the arrangement of these regions in the form of a regular spatial lattice allows heat to be effectively removed from them (these injection regions) through sub-barrier regions to a heat sink located on the cathode side. This ultimately allows for continuous operation of the inventive device, rather than pulsed.

A high-frequency Gunn effect device with a hetero injector (see Fig. 4) contains an active layer l of GaAs semiconductor material n of the conductivity type formed on it from the side of the anode contact 2 of the semiconductor layer 3 n ⁺⁺ of the conductivity type and from the cathode contact of the local cylindrical hetero injector , injecting current into the device, wherein geteroinzhektor successively composed of a layer 4 of semiconductor material with a larger bandgap than the material of n GaAs, for example, Al _x Ga _1-x As, contacting the one with Oron, l active layer of a semiconductor material and n GaAs forming the heterojunction with it sharp and the other side contacted with cloem Al _x Ga _1-x As of 5 with a decreasing value of the parameter x to zero towards conductivity type n ⁺⁺ layer 6, and layer of Al _x Ga _1-x As layer 5 is located between the material 4 Al _x Ga _1-x As with it and has the same value of the parameter x at the boundary contact, and n ⁺⁺ conductivity type layer 6. The cathode of the high frequency AC domain on the Gunn effect device with a hetero-injector consists of a current-injecting region (generator) AMNB and limiting the injection of current into the device region 7 BC. The limiting current injection into the device of region 7 BC is made in the form of a reverse-biased Schottky barrier.

наблюдается следующая картина. В начальный момент времени при подключении к высокочастотному прибору на эффекте Ганна с гетероинжектором постоянного напряжения нормальная составляющая поля у границы 6 проводящей части катода (см. фиг. 4) будет гораздо больше, чем аналогичное поле на аноде 2. Данное утверждение вытекает из следующих соображений:
1) эффективное значение барьера у ограничивающей ток части катода 7 выбрано таким, что исключает протекание тока через обратно-смещенный барьер Шоттки;
2) полный ток через боковые стенки ячейки прибора (фиг. 4) равен нулю;
3) ток, втекающий в проводящую ток часть катода 6 и вытекающий из анода в основном состоит из тока проводимости (как показали численные расчеты токами смещения и диффузии в первом приближении можно принебречь);
4) отношение площади инжектирующей ток части катода AB к общей площади катода составляет не более 10%
5) в начале момент времени после включения постоянного напряжения проводимость у инжектирующей ток части катода 6 изменяется незначительно;
6) ток через прибор в начальный момент времени после включения постоянного напряжения определяется последующей формулой:
I = σ•S_к•E $\genfrac{}{}{0ex}{}{\text{ср}}{\text{к}}$
где E $\genfrac{}{}{0ex}{}{\text{ch}}{\text{к}}$ нормальной составляющая среднего поля вдоль инжектирующей ток части катода;
S_k площадь инжектирующей ток части катода.The operation of the high-frequency device on the Gunn effect is as follows. When connected to a constant bias voltage

The following picture is observed. At the initial moment of time, when connected to a high-frequency device based on the Gunn effect with a constant voltage hetero injector, the normal field component at the boundary 6 of the conductive part of the cathode (see Fig. 4) will be much larger than the analogous field on anode 2. This statement follows from the following considerations:
1) the effective value of the barrier in the current-limiting part of the cathode 7 is chosen such that excludes the flow of current through the reverse-biased Schottky barrier;
2) the total current through the side walls of the device cell (Fig. 4) is equal to zero;
3) the current flowing into the conductive current part of the cathode 6 and flowing out of the anode mainly consists of the conduction current (as shown by numerical calculations, the bias and diffusion currents can be neglected to a first approximation);
4) the ratio of the area of the current-injecting part of the cathode AB to the total area of the cathode is not more than 10%
5) at the beginning of the time after the inclusion of a constant voltage, the conductivity of the current-injecting part of the cathode 6 changes slightly;
6) the current through the device at the initial time after the inclusion of a constant voltage is determined by the following formula:
I = σ • S _to • E $\genfrac{}{}{0ex}{}{\text{wed}}{\text{to}}$
where e $\genfrac{}{}{0ex}{}{\text{ch}}{\text{to}}$ the normal component of the mean field along the current-injecting part of the cathode;
S _{k the} area of the current-injecting part of the cathode.

где S_a площадь анода;
E $\genfrac{}{}{0ex}{}{\text{ch}}{\text{a}}$ нормальная составляющая среднего вдоль анодного контакта.Based on the foregoing, the fact follows that the average normal field E $\genfrac{}{}{0ex}{}{\text{ch}}{\text{to}}$ the injection part of the cathode 6 at the initial time after the inclusion of a constant voltage is determined as follows:

where S _{a is the} area of the anode;
E $\genfrac{}{}{0ex}{}{\text{ch}}{\text{a}}$ normal component of the mean along the anode contact.

The increased value of the normal field of the current-conducting part of the cathode 6 of the proposed device, together with the integrated field in the regions 4, 5 of the Al _x Ga _1-x As layer of the heteroinjector, create an increased value of the normal field E _out at the n ⁺ - Al _x Ga _1-x As heterointerface / n GaAs along the device between the hetero injector and the active region of ln GaAs. The specified field E _o at the initial time after the inclusion of constant inclusion leads to the appearance of a fixed enriched layer (OS) at the hetero injector and a moving enriched layer. The indicated OS correspond to field peaks in the claimed device. The mobile OS, having separated from the fixed OS at the hetero-injector at the beginning of the path, increases very quickly to a much larger volume than in the case of the formation of the OS in the device according to the prototype. When approaching the anode region, the enriched layer becomes wider, decreasing in amplitude. Note that in the case of the proposed device compared to the device of the prototype, the mobile OS passes a significantly smaller portion of the active region along the device before it becomes wider, decreasing in amplitude. The motion of a mobile OS is characterized by the movement of a field peak, the maximum of which corresponds to the leading edge of the mobile OS. After the transient is established in the device, a suprathreshold field is established with a small dip in the active region of the inventive device at the n ⁺ Al _x Ga _1-x As / n - GaAs heterointerface, which corresponds to a fixed OS, forming a small virtual cathode. Note that the existence of a virtual cathode indicates that the device is not optimized, however, the frequency range of the inventive device is more than two times wider compared to the frequency range of the prototype device (Fig. 10).

 After the mobile OS leaves the anode region, no new mobile OSs appear in the active region of the device, which would be characterized by the field pulsations described above, and the concentration of free carriers. When applied to the device as an external voltage, not only a constant component, but also a variable U = -Asinω • t, where A is the amplitude of the variable signal, ω is the circular frequency of this signal. The device generates microwave oscillations.

In FIG. 6, 7, 8 and 9, field distributions, carrier concentrations over a quarter of the period of the external signal along the active region of the inventive device are presented, starting from the n ⁺ -Al _x Ga _1-x As / n GaAs heterointerface to the anode as under the region of the device hetero injector under consideration ( Fig. 6 and 7), and under the barrier region (Fig. 8 and 9), which allow a better understanding of the proposed high-frequency device based on the Gunn effect with a hetero injector. Note that in the dynamic mode, the virtual cathode does not disappear (this can be clearly seen in the example of the distribution of the field under the injector along the device), which is confirmed primarily by the fact that the device is not optimized. In FIG. 10 (curves 1 and 2) presents the frequency dependences of the inventive device (Fig. 10, curve 1) and the prototype device (Fig. 10, curve 2), which confirm the fact that the requirements are met 1) 3) to the media parameters injected into the active area of the device leads to a significant increase in the efficiency of this device and the expansion of the frequency range of the considered inventive device compared with the device of the prototype.

, толщина слоя 5 Al_xGa_1-xAs l₂ 500

, толщина слоя 6 n типа проводимости l₁ (0.3 0.5) мкм. Концентрация носителей в слое 6 n⁺⁺ типа проводимости n⁺⁺ (1 4)•10¹⁸см^-3.Concrete example
ESAG GaAs substrates with a thickness of 250 μm with a crystallographic orientation of (100) were used as the semiconductor material, with the carrier concentration in the n ⁺⁺ layer of the region from the anode contact side being (1 4) • 10 ¹⁸ cm ^-3 , the carrier concentration in the active n layer ( 3 7) • 10 ¹⁵ cm. The thickness of the active n layer of GaAsl _{4 is} 0.72 μm, the thickness of layer 4 of Al _x Ga _1-x As material (see Fig. 4), l ₃ 1000

, layer thickness 5 Al _x Ga _1-x As l ₂ 500

, the thickness of the layer is 6 n type conductivity l ₁ (0.3 0.5) μm. The concentration of carriers in layer 6 is n ⁺⁺ of conductivity type n ⁺⁺ (1 4) • 10 ¹⁸ cm ^-3 .

, затем в едином технологическом цикле с помощью МЛЭ, уменьшая параметр x до 0, выращивают слой Al_xGa_1-xAs толщиной 500

. Далее, центрифугированием наносят на пластину слой фоторезиста толщиной 1 - 1.2 мкм. Сушка фоторезиста осуществляется в ИК-камере при Т (65 75)^oC. Затем осуществляется формирование окон под области, органичивающие инжекцию тока в прибор путем фотолитографии. Далее, через сформированные окна в полупроводниковой пластине формировались канавки с помощью селективного травителя состава H₂SO₄:H₂O₂:H₂O=1: 8: 10 при температуре 24^oC на глубину выращенных гетерослоев, то есть

Формирование канавок возможно также осуществить с помощью ионно-плазменного травления. Затем методом МЛЭ указанные заращиваются материалом того же состава и концентрации, как и активный n слой GaAs на всю их глубину. Формирование областей прибора, ограничивающих инжекцию тока в прибор, осуществлялось путем вакуумного напыления композиции AuGe (88% Au, 12% Ge) толщиной 600 1200

в области сформированные с помощью литографии и предназначенные для ограничения инжекции тока. Затем на всю поверхность пластины наносился второй слой композиции AuGe(88% Au, 12% Ge). Далее, наносился слой протекторного материала, например, Мо толщиной 1200 1400

и слой Au толщиной 1200 - 1400

, и слой Au толщиной 4000 5000

. Далее, в атмосфере водорода проводят термическую обработку при T 400 430^oC в течение 1 1.5 мин. С целью получения барьера Шоттки и омических контактов.Al _x Ga _1-x As material with a parameter of x 0.22 and a thickness of 1000 is grown on the entire GaAs substrate using molecular beam epitaxy (MBE)

then, in a single technological cycle using MBE, reducing the parameter x to 0, a 500 _x Al _x Ga _1-x As layer is grown

. Next, a layer of photoresist 1 - 1.2 μm thick is applied to the plate by centrifugation. Drying of the photoresist is carried out in an infrared camera at T (65 75) ^o C. Then, windows are formed under the region, limiting the current injection into the device by photolithography. Further, grooves were formed through the formed windows in the semiconductor wafer using a selective etchant of the composition H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 1: 8: 10 at a temperature of 24 ^o C to the depth of the grown heterolayers, i.e.

The formation of grooves can also be carried out using ion-plasma etching. Then, using the MBE method, these are overgrown with material of the same composition and concentration as the active n GaAs layer to their entire depth. The areas of the device that limit the injection of current into the device were formed by vacuum deposition of the AuGe composition (88% Au, 12% Ge) with a thickness of 600 1200

in areas formed by lithography and designed to limit current injection. Then, a second layer of the AuGe composition (88% Au, 12% Ge) was applied to the entire surface of the plate. Next, a layer of tread material was applied, for example, Mo with a thickness of 1200 1400

and Au layer 1200 - 1400 thick

and an Au layer 4000 4000 thick

. Further, in a hydrogen atmosphere, heat treatment is carried out at T 400 430 ^o C for 1 1.5 minutes In order to obtain a Schottky barrier and ohmic contacts.

 Temperature operating mode of the device is 77 K, the obtained frequency range is 100 250 GHz, efficiency 5.43%

Claims (3)

1. High-frequency device based on the Gunn effect, containing n-type GaAs semiconductor material, n ^{+ +} -GaAs-type semiconductor layers formed on it from the side of the anode contact and the local region of n ^{+ +} -GaAs-type conductivity in the areas of the cathode contact, injecting current, an anode contact, and a cathodic contact containing a first plurality of regions injecting current into the apparatus and a second plurality of regions restricting current injection into the apparatus, the regions injecting current into the apparatus form a planar lattice from ichayuschiysya in that the region of the cathode, inject a current into the device, are in the form of local geteroinzhektorov sequentially consisting of a semiconductor material with a larger bandgap than the material n-GaAs, Al _x Ga _{1 - x} As, with a constant value x parameter, contacting on the one hand the n-GaAs semiconductor material and forming a heterojunction with it, and on the other hand, it contacts the Al _x Ga _{1 - x} As layer with a decreasing value of the parameter x to zero in the direction to the n ^{+ +} -GaAs-type conductivity layer with side of the cathodic contact, with em layer with linearly changing value of the parameter x Al _x Ga _{1 - x} As located between the layer material Al _x Ga _{1 - x} As with a constant x value with it and has the same value of the parameter x in the boundary layer and contacting the n ^{+ +} -GaAs- of conductivity type, the hetero injector being surrounded by a region restricting the current injection made in the form of a reverse-biased Schottky barrier, and the parameter x is selected from the condition 0 <x ≅ 0.23, and the energy ε accumulated by the carriers along the length of the hetero injector satisfies the following relation:
ε ≅ ΔГL,
where ΔГL is the energy gap between the Г- and L-valleys of GaAs. 2. The device according to claim 1, characterized in that the concentration of carriers in the n-type layer satisfies the following ratio:
n ^{+ +} > n ⁺ > n,
where the concentration of n ^{+ +} and n are selected from the following conditions:
8 • 10 ^{1 7} ≅ n ^{+ +} ≅ 5 • 10 ^{1 8} , cm ^{- 3} ;
3 • 10 ^{1 5} ≅ n ≅ 1.4 • 10 ^{1 6} , cm ^{- 3} . 3. The device according to claims 1 and 2, characterized in that the sum of the length of the region with a ramp value of the parameter x Al _x Ga _{1 - x} As and the length of the region with a constant value of the parameter x Al _x Ga _{1 - x} As satisfy the following ratio:

4. The device according to paragraphs. 1 to 3, characterized in that the local heteroinjectors are made in the form of cylindrical regions directed deep into the semiconductor material, with the bases of the cylinders lying in the plane of the cathode contact of the device, and their generatrix perpendicular to the plane of the cathode contact.

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