Low-noise microwave field-effect transistor on semiconductor heterostructure
By incorporating specific quantum barrier layers and narrow-bandgap materials, the transistor's electron localization is enhanced, leading to improved gain and reduced noise figure, addressing performance limitations in microwave field-effect transistors for radar applications.
Patent Information
- Authority / Receiving Office
- RU · RU
- Patent Type
- Patents
- Current Assignee / Owner
- AKTSIONERNOE OBSHCHESTVO NAUCHNO PROIZVODSTVENNOE PREDPRIYATIE ISTOK IMENI A I SHOKINA
- Filing Date
- 2025-12-03
- Publication Date
- 2026-07-09
AI Technical Summary
Existing microwave field-effect transistors on semiconductor heterostructures face limitations in gain and noise figure, particularly in low-noise radar applications, due to insufficient electron localization and scattering from doping impurities, which restrict their performance in high-frequency operations.
The introduction of additional quantum barrier layers of i-AlAs and specific narrow-bandgap materials with controlled thickness and composition between the channel and gate layers, forming a sequence of barrier, transition, and contact layers, enhances electron localization and reduces scattering, thereby increasing gain and decreasing noise figure.
This configuration results in a significant increase in gain (up to 16.8 dB) and a reduction in noise figure (to 0.25 dB) at 10 GHz, improving the transistor's performance for low-noise radar applications.
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Abstract
Description
[0001] The invention relates to microwave electronics, namely microwave field-effect transistors on a semiconductor heterostructure, and is intended for the development and production of a wide class of microwave electronics devices, including microwave radar devices.
[0002] Significant progress in improving the electrical parameters of microwave field-effect transistors on a semiconductor heterostructure is provided by so-called high electron mobility transistors (HEMT).
[0003] The conduction region in these transistors consists of a wide-bandgap layer doped with donor impurities and an undoped narrow-bandgap layer. This provides a significant increase in operating frequency to 100 GHz, a gain of up to 10 dB at an operating frequency of 10 GHz, and a reduction in noise figure to less than 1 dB.
[0004] A low-noise microwave field-effect transistor is known on a semiconductor heterostructure, containing a semiconductor substrate and a sequence of at least one layer of wide-band and one layer of narrow-band material with specified characteristics of a semiconductor heterostructure of the AlGaAs-GaAs-AlGaAs type, source, gate, and drain electrodes located on the outer surface of the semiconductor heterostructure, in which, in order to increase the gain and reduce the noise figure, the said semiconductor heterostructure is made in the form of a sequence of the following main layers: at least one GaAs buffer layer with a thickness of at least 200 nm, a group of conductive layers that form a channel of the field-effect transistor, consisting of the actual GaAs channel layer with a thickness of 10-20 nm and at least two layers doped with a donor impurity δn with a surface donor density of (1-2)×10 12 cm -2 and two spacer i layers of Al x Ga 1-xAs with a thickness of each 1-3 nm, located in pairs on both sides of the actual channel layer, two groups of barrier layers Al x Ga 1-x As, and in the spacer layer on the gate side, to increase the electron mobility, a quantum barrier of AlAs with a thickness of 2-18 nm is introduced, the Al layer x Ga 1-x As located between the δn layer and the gate, the ohmic contact layer n + -GaAs source and drain electrodes with a thickness of (10-60) nm [See A.N. Vinichenko, V.P. Gladkov, N.I. Kargin, M.N. Strikhanov, I.S. Vasilievsky. “Increasing the Electron Mobility in HEMT Heterostructures with a Composite Spacer Containing AlAs Nanolayers” / / Semiconductor Physics and Technology, 2014, Vol. 48, Issue 12, pp. 1660-1665].
[0005] This microwave field-effect transistor features a relatively high gain (approximately 12.0 dB when configured for minimum noise figure) at an operating frequency of 10 GHz and low noise (approximately 0.7 dB). However, these gain and noise levels are insufficient in some cases and significantly limit its application.
[0006] The closest to the claimed invention is a high-power microwave field-effect transistor on a semiconductor heterostructure, containing a semiconductor substrate, a buffer layer, a sequence of layers of wide-bandgap and a layer of narrow-bandgap materials of the AlGaAs-InGaAs-GaAs type with specified characteristics, wherein the groups of conductive layers forming the channel contain at least one In layer y Ga1_ yAs with different values for the chemical element, at least two δn-layers doped with a donor impurity, at least two spacer i-layers located in pairs on both sides of the channel layer, two groups of Al barrier layers x Ga 1-x As, each in the form of a system of barrier layers, one of which is located on one side of the group of conductive layers above the substrate - the substrate, the other - on the opposite side - the gate, while the substrate is made in the form of an acceptor-donor system of barrier layers Al x Ga 1-x The As source, gate, and drain electrodes are located on the outer surface of the semiconductor heterostructure. The gate barrier layer group is implemented as a donor-acceptor system of Al barrier layers. x Ga 1-x As or unalloyed system of barrier layers Al x Ga 1-xAs, the substrate and gate groups of barrier layers of the semiconductor heterostructure additionally contain at least two barrier layers of i-AlAs with a thickness of 2-6 atomic monolayers each, wherein in each mentioned group of barrier layers, which are separated from each other by a layer of narrow-bandgap material Al x Ga 1-x As with a molar fraction x of the chemical element Al less than 0.4, with a thickness of more than 3 atomic monolayers [RU Patent for Invention No. 2799735 “Powerful microwave field-effect transistor on a semiconductor heterostructure” / Pashkovsky A.B. et al. / / Bulletin No. 20, 11.07.2023, accepted as a prototype].
[0007] This microwave field-effect transistor, when designed in a low-noise version (gate width 75 μm), has a fairly high gain (approximately 13.5 dB when configured for minimum noise figure) at an operating frequency of 10 GHz, and a fairly low noise figure of 0.8 dB, however, due to the scattering of hot electrons from the channel on the doping ionized impurities on the substrate side when the device operates in low-noise mode, the achievable levels of gain and noise figure are insufficient for use in low-noise radar amplifiers.
[0008] The technical result of the declared low-noise microwave field-effect transistor on a semiconductor heterostructure is an increase in the gain factor and a decrease in the noise figure.
[0009] The specified technical result is achieved in that in a low-noise microwave field-effect transistor on a semiconductor heterostructure, containing a semiconductor substrate and a sequence of at least one layer of wide-band and one layer of narrow-band semiconductor heterostructure material with specified characteristics, in the form of a buffer layer, a group of conductive layers that form a channel of the field-effect transistor, as part of the actual channel layer consisting of one or more In layers y Ga 1-y As, at least one layer doped with a donor impurity and, or a δn-layer and an undoped spacer i-layer located between the channel layer itself and the doped layers, a group of barrier layers Al x Ga 1-xAs, in the form of a system of barrier layers located between the layer doped with donors and the gate, the source, gate, and drain electrodes, made according to a given topology of the field-effect transistor, while in the semiconductor heterostructure, at least three quantum barrier layers of i-AlAs are additionally made, each with a thickness of 2-6 atomic monolayers, wherein each of the said quantum barrier layers is located between the actual channel layer of In y Ga 1-y As either a group of layers of the latter and a gate, with at least one quantum barrier layer located between the doped layer and, or the δn-layer and the actual channel layer In y Ga 1-y As or a group of layers of the latter and at least one quantum barrier layer is located between the doped layer and, or the δn-layer and the gate, wherein the quantum barrier layers are separated from each other by at least one layer of narrow-bandgap material Al x Ga 1-xAs, with a mole fraction of the chemical element Al x less than 0.4, with a thickness equal to or greater than 2 atomic monolayers, or a GaAs layer with a thickness equal to or greater than 2 atomic monolayers, between the In channel layer itself y Ga 1-y GaAs layers, transition layers, i-AlAs quantum barrier layers, barrier layers, and layers doped with an acceptor impurity are formed as either a group of layers of the last layer and a buffer layer. The last layer of the barrier layer group can be formed in a given sequence: i-AlAs quantum barrier layers, barrier layers, transition layers, and contact layers.
[0010] The essence of the invention is as follows. Reducing the number of i-AlAs quantum layers to less than three is impractical due to a significant reduction in electron localization in the channel, resulting in a decrease in electron mobility, a decrease in gain, and an increase in noise figure.
[0011] Placing narrower (less than 2 atomic monolayers) or wider (more than 6 atomic monolayers) i-AlAs barrier layers between the gate and the channel of the semiconductor heterostructure is impractical due to changes in the properties of the potential barrier, and does not lead to the achievement of the technical result.
[0012] Implementation of the gate group of barrier layers in the form of a system of Al barrier layers x Ga 1-x As, in which there is at least one quantum barrier layer located between the doped layer, and either the δn layer and the In channel layer itself y Ga 1-y As, or a group of In layers y Ga 1-y As and at least one quantum barrier layer located between the doped layer and / or 5*n layer and the gate, wherein the quantum barrier layers are separated from each other by at least one layer of narrow-bandgap Al material x Ga 1-xAs, with a mole fraction of the chemical element Al x less than 0.4, with a thickness equal to or greater than 2 atomic monolayers, or a GaAs layer with a thickness equal to or greater than 2 atomic monolayers, provides an increase in the localization of electrons (up to 98.0 percent) in the region of the channel layer itself in the form of at least one In layer y Ga 1-y As, which leads to an increase in the saturation current of the field-effect transistor and, as a consequence, to a decrease in the resistance of the ohmic section of the source-gate, an increase in the drift velocity of electrons under the gate due to a decrease in scattering in the wide-bandgap material when operating in low-noise mode (high voltages on the gate) and, accordingly, an increase in the operating frequency of the transistor, its gain and a decrease in the noise figure compared to the prototype.
[0013] Made a layer of narrow-bandgap Al material x Ga 1-x As with a mole fraction of the chemical element Al хmore than 0.4 leads to a significant negative change in the physical properties of the above-mentioned material and a sharp decrease in the operating current in the group of conductive layers.
[0014] Making a separating layer of narrow-bandgap GaAs or Al material x Ga 1-x As with a mole fraction of the chemical element Al х less than 0.4 with a thickness of less than 2 atomic monolayers is undesirable due to the reduction in functionality (separation properties) of the narrow-bandgap Al material layer x Ga 1-x As.
[0015] Execution between the actual channel layer In y Ga 1-y As or a group of layers of the latter and a buffer layer of GaAs layers, transition layers, quantum barrier layers of i-AlAs, barrier layers, and layers doped with an acceptor impurity leads to an increase in the localization of electrons in the channel, accordingly a decrease in the cutoff voltage and an increase in the slope at low currents and, accordingly, an increase in the gain and a decrease in the noise figure.
[0016] The implementation of a group of barrier layers in a given sequence of i-AlAs quantum barrier layers, barrier, transition and contact layers on the last layer increases the localization of electrons in the channel with high electron mobility, reduces the number of defects in the structure, reduces the resistance of ohmic contacts and, as a consequence, leads to an increase in the gain and a decrease in the noise figure.
[0017] Thus, the essential features of the invention formula of a low-amplitude microwave field-effect transistor on a semiconductor heterostructure of the AlGaAs-InGaAs-GaAs type, each individually and in combination, ensure an increase in the gain factor and a decrease in the noise figure, that is, the achievement of the declared technical result.
[0018] The invention is explained by drawings.
[0019] Fig. 1 shows a fragment of the claimed low-noise microwave field-effect transistor on a semiconductor heterostructure, where:
[0020] - semiconductor substrate - 1,
[0021] - buffer layer - 2,
[0022] - a sequence of at least one layer of wide-bandgap and one layer of narrow-bandgap materials of a semiconductor heterostructure, with specified characteristics - 3 in the form:
[0023] - groups of conductive layers - 4, forming a channel of a field-effect transistor, as part of the actual channel layer in the form of at least one In layer y Ga 1-y As, with different values of the chemical element In,
[0024] - layer of narrow-band i-GaAs material between the channel and the buffer - 5,
[0025] - donor impurity doped δn-layer - 6
[0026] - undoped spacer i-layer - 7,
[0027] - barrier layer groups - 8,
[0028] - source electrodes - 9,
[0029] - gate electrodes-10,
[0030] - drain electrodes - 11,
[0031] - three barrier layers of i-AlAs - 12 (a, 6, b),
[0032] - four layers of narrow-bandgap i-GaAs material - 13 (a, 6, c, d),
[0033] - unalloyed i-Al layer 0,3 Ga 0,7 As - 14,
[0034] - acceptor impurity doped layer p + -Al 0,3 Ga 0,7 As - 15,
[0035] - unalloyed i-Al layer 0,3 Ga 0,7 As - 16,
[0036] - additional barrier layer -AlAs - 17,
[0037] - undoped i-GaAs layer - 19,
[0038] - additional barrier layer -AlAs - 18,
[0039] - i-Al transition layer 0,1 Ga 0,9 As - 20,
[0040] - barrier layer - 21,
[0041] - contact layers - 22.
[0042] The device operates as follows. A signal is applied to the gate electrode 10, and a constant voltage is applied to the source electrode 9 and drain electrode 11. The gate signal modulates the surface density of electrons in channel 4 of the transistor, which is formed on heterostructure 3. Heterostructure 3 is formed on semiconductor substrate 1 with buffer layer 2 and includes a layer of narrow-gap i-GaAs material between the channel and the buffer 5, a donor-doped δn-layer 6, an undoped spacer i-layer 7, and a group of barrier layers 8. The introduction of three additional i-AlAs barrier layers 12 (a, b, c) and four layers of narrow-gap i-GaAs material 13 (a, b, c, d) into the heterostructure makes it possible to increase the surface density of electrons in the channel without reducing their mobility, which leads to an increase in the transistor current and, accordingly, its gain when operating in low-noise mode and a decrease in the noise figure. The amplified signal is read from drain electrode 11.
[0043] Introduction between the actual channel layer In y Ga 1-y As either a group of layers of the latter and a buffer layer of the i-Al barrier layer 0,3 Ga 0,7 As-14, acceptor-doped layer p + -Al 0,3 Ga 0,7 As-15 and unalloyed i-Al layer 0,3 Ga 0,7 As-16 (Fig. 1) leads to an increase in the localization of electrons in the channel, accordingly a decrease in the cutoff voltage and an increase in the slope at low currents and, accordingly, an increase in the gain and a decrease in the noise figure.
[0044] The implementation of a low-noise microwave field-effect transistor (Fig. 1) with the introduction of an additional barrier layer -AlAs - 17 and the implementation on the last layer of a group of barrier layers in a given sequence: an additional barrier layer -AlAs - 18, an undoped layer of i-GaAs - 19, a transition layer of i-Al 0,1 Ga 0.9As - 20, barrier layer - 21, contact layers - 22 allows to increase the localization of electrons in the channel with high electron mobility, reduces the number of defects in the structure, reduces the resistance of ohmic contacts and, as a consequence, leads to an increase in the gain and a decrease in the noise figure.
[0045] The gain and noise figure were calculated for various variants of the low-noise microwave field-effect transistor listed below. The gain and noise figure were calculated using the model [See A.B. Pashkovsky, A.S. Bogdanov, V.M. Lukashin, S.I. Novikov "Nonlocal Electron Dynamics in Transistor Heterostructures with Donor-Acceptor Doping" / / Microelectronics, 2020, Vol. 49, No. 3, pp. 210-225].
[0046] Example 1. A low-noise microwave field-effect transistor based on a semiconductor heterostructure is manufactured using traditional (classical) manufacturing methods (processes) for thin-film technology. The low-noise microwave field-effect transistor is designed as follows (Fig. 1). The following are formed on a 100-μm-thick gallium arsenide GaAs 1 semiconductor substrate:
[0047] - buffer layer 2, in the form of a GaAs-Al system x Ga 1-x As layers,
[0048] - a sequence of at least one layer of wide-bandgap and one layer of narrow-bandgap materials of a semiconductor heterostructure, with specified characteristics - 3 in the form:
[0049] - groups of conductive layers that form the channel of a field-effect transistor, as part of the actual channel layer in the form of one InyGa layer 1-y As-4, and GaAs(y=0) layers - 5,
[0050] - donor impurity doped δn-layer (silicon Si) - 6 and undoped spacer i-layer - 7 located between the channel and doped layer 6,
[0051] - barrier layer groups - 8, in the form of a barrier layer system,
[0052] - source, gate, drain electrodes - 9, 10, 11 respectively, located on the outer surface of the semiconductor heterostructure 3,
[0053] - three barrier layers i-AlAs - 12 (a, 6, b), located in a group of barrier layers,
[0054] - four layers of narrow-band i-GaAs material - 13 (a, 6, c, d), one located between the barrier layers respectively,
[0055] - unalloyed i-Al layer 0,3 Ga 0,7 As - 14,
[0056] - acceptor impurity doped layer p + -Al 0,3 Ga 0,7 As - 15,
[0057] - unalloyed i-Al layer 0,3 Ga 0,7 As - 16.
[0058] - additional barrier layer -AlAs - 17,
[0059] - additional barrier layer -AlAs - 18,
[0060] - undoped i-GaAs layer - 19,
[0061] - i-Al transition layer 0,1 Ga 0,9 As - 20,
[0062] - barrier layer - 21,
[0063] - contact layers - 22.
[0064] Examples 2-5. Variants of a low-amplitude microwave field-effect transistor similar to example 1, but with different design parameters: according to the invention formula (examples 2 and 5) and beyond it (examples 3 and 4).
[0065] Example 6 corresponds to the prototype sample.
[0066] The data for samples 1-5 are summarized in Table 1. The analysis of the obtained results showed that the samples of the low-noise microwave field-effect transistor designed according to the claimed technical solution (examples 1, 2, 5) have gain values at the level of (14.5-16.8 dB) and a noise figure at the level of 0.5-0.25 dB, while the samples according to examples 4 and 5 have gain values at the level of (13.5-13.0) dB and a noise figure of 0.6-0.8 dB.
[0067] Thus, the declared low-noise microwave field-effect transistor on a semiconductor heterostructure of the AlGaAs-InGaAs-GaAs type, in comparison with the prototype, will provide an increase in the gain factor with a decrease in the noise figure.
Claims
A low-noise microwave field-effect transistor on a semiconductor heterostructure, comprising a semiconductor substrate and a sequence of at least one layer of wide-bandgap and one layer of narrow-bandgap semiconductor heterostructure material with specified characteristics, in the form of a buffer layer, a group of conductive layers forming a channel of the field-effect transistor, as part of the channel layer itself consisting of one or more In layers y Ga 1-y As, at least one layer doped with a donor impurity and, or a δn-layer and an undoped spacer i-layer located between the channel layer itself and the doped layers of the group of Al barrier layers x Ga 1-xAs, in the form of a system of barrier layers located between the layer doped with donors and the gate, the source, gate, and drain electrodes, made according to a given topology of the field-effect transistor, characterized in that at least three quantum barrier layers of i-AlAs are additionally made in the semiconductor heterostructure, each with a thickness of 2-6 atomic monolayers, wherein each of the said quantum barrier layers is located between the actual channel layer of In y Ga 1-y As either a group of layers of the latter and a gate, with at least one quantum barrier layer located between the doped layer and, or the δn-layer and the actual channel layer In y Ga 1-y As or a group of layers of the latter and at least one quantum barrier layer is located between the doped layer and, or the δn-layer and the gate, wherein the quantum barrier layers are separated from each other by at least one layer of narrow-bandgap material Al x Ga 1-xAs, with a mole fraction of the chemical element Al x less than 0.4, with a thickness equal to or greater than 2 atomic monolayers, or a GaAs layer with a thickness equal to or greater than 2 atomic monolayers, between the In channel layer itself y Ga 1-y As either a group of layers of the last and a buffer layer, GaAs layers, transition layers, quantum barrier layers of i-AlAs, barrier layers, and layers doped with an acceptor impurity are made; on the last layer of the group of barrier layers, quantum barrier layers of i-AlAs, barrier, transition and contact layers are made in a given sequence.