High electron-mobility heterostructures of double continuous gradient back-barrier group III nitrides

Abstract

The present invention relates to a high electron-mobility heterostructure and a method for manufacturing a heterostructure, wherein the high electron-mobility heterostructure comprises a substrate, a buffer on the substrate, a doped charge compensation layer on the buffer, a double continuous gradient barrier on the doped charge compensation layer having increasing and decreasing polarization charges, a channel on the double continuous gradient barrier, and a charge generation layer on the channel. The method includes forming a substrate, forming a buffer on the substrate, forming a doped charge compensation layer on the buffer, forming a double continuous gradient barrier on the doped charge compensation layer, forming a channel on the double continuous gradient barrier, and forming a charge generation layer on the channel.

Description

Background Art

[0001] Next-generation high-charge and high-electron-mobility devices (e.g., high-electron-mobility transistors (HEMTs) and diodes) are currently plagued by increased leakage current due to insufficient electron confinement. Current scandium aluminum nitride (ScAlN)-based HEMTs have high buffer leakage with their high charge density. The high buffer leakage may be due to insufficient confinement on the back side of the two-dimensional electron gas (2DEG). The buffer leakage can be two to three orders of magnitude higher than that of aluminum gallium nitride (AlGaN)-based gallium nitride (GaN) HEMTs. Higher buffer leakage reduces radio frequency (RF) efficiency and increases power loss.

[0002] FIG. 1 is a diagram of an exemplary prior art HEMT heterostructure 100 having a single back barrier layer. FIG. 2 is a diagram of an exemplary prior art HEMT heterostructure 200 having a single back barrier layer and a transition layer. FIG. 3 is a chart of the energy and free carrier density positions of the exemplary prior art HEMT heterostructures of FIGS. 1 and 2, showing parasitic 2DEGs. The parasitic 2DEGs increase the leakage current of the HEMT device and reduce the maximum power. Current back barrier HEMT heterostructures do not completely eliminate parasitic 2DEGs without requiring tight tolerances on the dimensions of the heterostructure or without reducing the back barrier tilt.

[0003] FIG. 4 is a diagram of an exemplary prior art HEMT heterostructure 400 having two back barriers. Each back barrier includes AlGaN and has a single fixed percentage concentration of aluminum (Al), and the first back barrier has a lower Al concentration than the second back barrier. FIG. 5 is a chart of the exemplary HEMT heterostructure of FIG. 4 where the first back barrier has a fixed 2% concentration of Al and the second back barrier has a fixed 5% concentration of Al.

[0004] Achieving precise in-plane lattice matching conditions is difficult in heterojunctions with epitaxial growth, and consequently, some degree of in-plane mismatch usually exists between different layers. When an epitaxial layer grows on a crystalline substrate or on one or more epitaxial layers with defined crystallinity, the in-plane lattice of the epitaxial layer initially fits to match the in-plane lattice parameters of the underlying material. However, as the epitaxial layer attempts to fit to the underlying in-plane lattice, it experiences tensile or compressive in-plane strain, and the strain energy of the epitaxial layer increases until it becomes large enough to nucleate misfit dislocations. The formation of misfit crystalline dislocations reduces the strain in the epitaxial layer, allowing the in-plane lattice parameters to relax above the interface toward its bulk lattice structure. The thickness at which misfit dislocations nucleate to relax the strain in the epitaxial layer is known as the critical thickness of the layer. The larger the in-plane lattice mismatch, the smaller the critical thickness of the epitaxial layer. When the thickness of the epitaxial layer is less than the critical thickness, the epitaxial layer is said to be pseudo-lattice-matched. In group III nitride-based transistors, a nearly identical in-plane lattice across various layers is desired to minimize misfit dislocations and defect formation. [Overview of the Initiative]

[0005] According to the concepts described herein, exemplary heterostructures and methods provide a pair of continuous-gradient pseudolattice-matched back barrier layers that enable a remarkably steep conduction band gradient below the channel without forming parasitic 2DEGs, thereby improving electron confinement.

[0006] According to the concepts described herein, exemplary heterostructures and methods provide a pair of pseudo-lattice-matched back barrier layers, one of which is continuously gradient from the buffer material toward a group III nitride (III-N) alloy, and the other of which is continuously gradient from the III-N alloy toward a channel material.

[0007] Methods and processes for forming and using the disclosed embodiments can be understood by referring to the drawings in the accompanying drawings. It should be understood that the components and structures shown in the drawings are not necessarily to scale, and instead the emphasis is on illustrating the principles of the concepts described herein. Similar reference numerals indicate corresponding parts across different drawings. Furthermore, embodiments are shown in the drawings as examples, not limitations. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram of an exemplary prior art HEMT heterostructure having a single back barrier. [Figure 2] This is a diagram of an exemplary prior art HEMT heterostructure having a single back barrier and transition layer. [Figure 3] Figures 1 and 2 show the relationship between energy and free carrier density at location for exemplary conventional HEMT heterostructures. [Figure 4] This is a diagram of an exemplary prior art HEMT heterostructure having two back barriers, each having a fixed percentage concentration of Al. [Figure 5] Figure 4 shows the fixed percentage of Al concentration in each of the two back barriers of the conventional HEMT heterostructure. [Figure 6A] This is a diagram of an exemplary high-electron-mobility heterostructure in the present disclosure. [Figure 6B] Figure 6A shows an example of a high electron mobility device configured as a HEMT. [Figure 6C] Figure 6A shows an example of a high-electron-mobility device configured as a diode. [Figure 7A] Figure 6A shows a graph of the continuous Al concentration percentages in each of the two back barriers of an exemplary high-electron-mobility heterostructure. [Figure 7B] Figure 6A shows the continuous polarization gradients in each of the two back barriers of another exemplary high-electron-mobility heterostructure. [Figure 8]This is a diagram showing the position of energy and free carrier density for exemplary high-electron-mobility heterostructures of the present disclosure. [Figure 9] This is a diagram of a first alternative exemplary high-electron-mobility heterostructure of the present disclosure. [Figure 10] This is a diagram of a second alternative exemplary high-electron-mobility heterostructure of the present disclosure. [Figure 11] This is a diagram of a third alternative exemplary high-electron-mobility heterostructure of the present disclosure. [Figure 12] This is an exemplary method for producing the high electron mobility heterostructure of the present disclosure. [Modes for carrying out the invention]

[0009] This disclosure provides a pair of pseudo-lattice-matched back barrier layers, one of which is continuously gradient from the buffer material toward a group III nitride (III-N) alloy, and the other of which is continuously gradient from the III-N alloy toward a channel material. The gradient in the material generates a quasi-electric field that influences the shape of the energy barrier to electrons. A certain amount of doping is added to the buffer material immediately beneath the pair of pseudo-lattice-matched back barrier layers to compensate for the quasi-electric field generated by the changing polarization of the pair of back barrier layers. The two continuous gradients of the pair of back barrier layers, and the compensatory doping in the buffer material, form the barrier in a favorable manner by increasing 2DEG confinement through a higher back barrier conduction band gradient. Polarization in semiconductors is caused by the asymmetry of electron clouds in the crystal lattice. The polarization charge is the sum of the spontaneous polarization charge and the piezoelectric polarization charge. The piezoelectric polarization charge is induced by strain applied to the material through the piezoelectric effect. Crystals can have tensile or compressive strain by being grown pseudo-lattice-matched using materials with larger or narrower lattice constants. The amount of piezoelectric polarization charge depends on the lattice constant of the material, the lattice constant of the surrounding material, and the strain, which is a function of the degree to which this difference deforms the crystal. Spontaneous polarization charge is a dipole charge induced by the intrinsic asymmetry of the crystal lattice. This exists in crystals having a wurtzite structure due to its asymmetry in the c-direction of the crystal, and its value varies depending on the constituent atoms and their composition ratio. A continuous polarization gradient in a material is one in which the material composition of the crystal is gradually adjusted as the crystal grows, and the polarization charge in the gradient also changes in a gradual manner from one material composition to the next. An exemplary continuous polarization gradient can be formed by changing the percentage of Al in the AlGaN layer as the AlGaN layer grows.

[0010] Figure 6A is a diagram of an exemplary high electron-mobility heterostructure 600 of the present disclosure. In an exemplary embodiment, the high electron-mobility heterostructure 600 comprises a substrate 601, a buffer 603 on the substrate 601, a double continuous gradient back barrier 605 on the buffer 603, a channel 607 on the double continuous gradient back barrier 605, and a charge generation layer 609 on the channel 607.

[0011] Buffer 603 may be doped near the boundary between buffer 603 and the double continuous gradient back barrier 605. Doping within buffer 603 near the double continuous gradient back barrier allows for belt bending there, thereby setting the depletion depth within buffer 603.

[0012] The double continuous gradient back barrier 605 features a pair of continuous gradient pseudo-lattice-matched back barrier layers that allow for a significantly steeper conduction band gradient below the channel 607 without parasitic 2DEGs, compared to conventional HEMT heterostructures, and the steeper conduction band gradient improves 2DEG confinement. The double continuous gradient back barrier 605 has a compositional profile that increases the conduction band gradient within the channel 607 and higher tolerances to the heterostructure dimensions that allow for the tunability of the high electron mobility heterostructure 600. For example, the high electron mobility heterostructure 600 can have an increased back barrier gradient, a thicker barrier, or a narrower channel while preventing parasitic 2DEGs. Between the pair of back barrier layers, there is a change in the direction of the gradient (e.g., the direction of change in Al percentage, or the direction of change in polarization charge). However, each of the pairs of back barrier layers is continuous independently of each other. The double continuous gradient back barrier is gradient in two directions of change in polarization charge. For example, the lower layer of a pair of back barrier layers is continuously sloped so that the polarization charge becomes more positive or increases in the growth direction, while the upper layer of the pair of back barrier layers shown in Figure 9 is continuously sloped so that the polarization charge becomes more negative or decreases in the growth direction (for example, as shown in Figure 7B).

[0013] The double polarization gradient in the present disclosure can be, for example, two adjacent independent continuous polarization gradients. The first polarization gradient (e.g., the lower back barrier 907 shown in FIG. 9) can have, for example, polarization charges that monotonically change across the entire first polarization gradient. The second polarization gradient (e.g., the upper back barrier 907 shown in FIG. 9) can have, for example, polarization charges that monotonically change across the entire second polarization gradient and have a direction of change opposite to that of the first polarization gradient. The polarization gradient can change monotonically (e.g., change in a way that consistently and gradually produces higher or lower values without reversing).

[0014] FIG. 6B is a diagram of an exemplary high electron mobility device of FIG. 6A configured as a HEMT. In the exemplary HEMT 600, contacts 611, 613, and 615 are provided for the source, gate, and drain of the HEMT 600, respectively.

[0015] FIG. 6C is a diagram of an exemplary high electron mobility device of FIG. 6A configured as a diode. In the exemplary diode 600, contacts 617 and 619 are provided for the anode and cathode of the diode 600, respectively.

[0016] FIG. 7A is a chart of the continuous Al concentration percentage in the exemplary double continuous gradient back barrier 605 of FIG. 6A. The double continuous gradient back barrier 605 comprises a pair of back barriers, each of the pair of back barriers having a continuous gradient of Al percentage, and the gradient directions of the polarization charges in each of the two back barriers are opposite to each other. For example, FIG. 7A shows that the lower back barrier of the double continuous gradient back barrier 605 in the AlGaN back barrier is graded from 0% Al to a positive rational percentage of Al, which will be described in more detail below with reference to FIGS. 9, 10, and 11. The upper back barrier of the double continuous gradient back barrier 605 in the AlGaN back barrier is graded from a positive rational percentage of Al to 0% Al, which will also be described in more detail below with reference to FIGS. 9, 10, and 11.

[0017] FIG. 7B is a diagram of the continuous change of polarization charge in another exemplary double - continuous - gradient back - barrier 605 of FIG. 6A. The double - continuous - gradient back - barrier 605 comprises a pair of back - barriers, each of the pair of back - barriers has a continuous gradient of polarization charge, and the gradient directions of the polarization charge in each of the two back - barriers are opposite to each other. For example, FIG. 7B shows that the lower back - barrier of the double - continuous - gradient back - barrier 605 increases in polarization charge, which will be described in more detail below with reference to FIGS. 9, 10, and 11. The upper back - barrier of the double - continuous - gradient back - barrier 605 decreases in polarization charge, which will also be described in more detail below with reference to FIGS. 9, 10, and 11.

[0018] FIG. 8 is a diagram of the energy and free - carrier density versus position of the exemplary high - electron - mobility heterostructure of FIG. 6A. This diagram is for an exemplary embodiment of a GaN / AlGaN double - continuous - gradient back - barrier / GaN heterostructure having a linear 0~10%~0% AlGaN gradient. That is, the exemplary embodiment has a lower back - barrier of a double - continuous - gradient back - barrier with an exemplary Al percentage linearly graded from 0% to 10% and an upper back - barrier of a double - continuous - gradient back - barrier with an exemplary Al percentage linearly graded from 10% to 0%.

[0019] Figure 9 shows an exemplary high electron-mobility heterostructure 900 of the first alternative of the present disclosure. The exemplary high electron-mobility heterostructure 900 comprises a substrate 901, a buffer 903 on the substrate 901, a doped charge compensation layer 905 on the buffer 903, a lower continuous gradient back barrier 907 having a continuously increasing (e.g., monotonically increasing) polarization charge on the doped charge compensation layer 905, an upper continuous gradient back barrier 909 having a continuously decreasing (e.g., monotonically decreasing) polarization charge on the lower continuous gradient back barrier 907, an unintentionally doped (UID) channel 911 on the upper continuous gradient back barrier 909, and a charge generation layer 913 on the UID channel 911. Optionally, there may be at least one of the following: a nucleation layer 915 between the substrate 901 and the buffer 903, at least one intermediate layer 917 between the UID channel 911 and the charge generation layer 913, and at least one capping layer 919 on the charge generation layer 913. The lower continuous gradient back barrier 907, the upper continuous gradient back barrier 909, the intermediate layer 917, the charge generation layer 913, and the capping layer 919 each include a pseudo-lattice-matched strain layer.

[0020] The substrate 901 may be silicon (Si), silicon carbide (SiC), sapphire, GaN, AlN, diamond, boron nitride (BN), or any other suitable substrate (e.g., SiC). The buffer 903 may be GaN or AlN, or any other suitable material (e.g., GaN).

[0021] The lower continuous gradient back barrier 907 may have a thickness greater than 3 nm. In exemplary embodiments where the lower continuous gradient back barrier 907 contains Al (e.g., AlGaN), the percentage of Al in the lower continuous gradient back barrier 907 may be continuously gradient from the range of 0-5%Al and increase to the range of 2-30%Al (e.g., monotonically increasing). In exemplary embodiments where the lower continuous gradient back barrier 907 contains indium (In) but does not contain Al (e.g., a back barrier of InGaN), the percentage of In in the lower continuous gradient back barrier 907 may be continuously gradient from the range of 5-100%In and decrease to the range of 0-95%In (e.g., monotonically decreasing). The upper continuous gradient back barrier 909 may have a thickness greater than 3 nm. In exemplary embodiments where the upper continuous gradient back barrier 909 contains Al, the percentage of Al in the upper continuous gradient back barrier 909 may be continuously gradient from the range of 2-30%Al and decrease to the range of 0-5%Al (e.g., monotonically decreasing). In an exemplary embodiment where the upper continuous gradient back barrier 909 contains indium (In) but not Al (e.g., an InGaN back barrier), the percentage of In in the upper continuous gradient back barrier 909 can be continuously gradient from a range of 0 to 95% In (e.g., GaN) and increase (e.g., monotonically) to a range of 5 to 100% In (e.g., InGaN). That is, the lower continuous gradient back barrier 907 and the upper continuous gradient back barrier 909 are gradient in opposite directions to each other. The lower continuous gradient back barrier 907 and the upper continuous gradient back barrier 909 may each be gradiented to the same material percentage (e.g., 0% to 100% Al or In) but in opposite directions (e.g., 0% to 100% Al or In vs. 100% to 0% Al or In), or to different material percentages (e.g., 0% to 100% Al or In vs. 95% to 5% Al or In) but in opposite directions (e.g., 0% to 100% vs. 95% to 5%). The total thickness of the lower continuous gradient back barrier 907 and the upper continuous gradient back barrier 909 may be the same or different, and less than the critical thickness for relaxation. In the growth of a pseudo-lattice-matched strain layer, the critical thickness is the thickness beyond which relaxation does not occur, and beyond which relaxation occurs due to misfit dislocation formation.

[0022] The UID channel 911 may be GaN, AlGaN, or InGaN, and may have a thickness in the range of 5 nm to 200 nm. 2DEG can be induced in the UID channel 911 by the charge generation layer 913. The charge generation layer 913 may be AlGaN, ScAlN, InAlN, InGaAlN, or AlN. At least one intermediate layer 917 may be AlN or GaN. The capping layer 919 may be GaN, AlN, or SiN. x This is also acceptable, where x is a positive rational number.

[0023] Figure 10 is a diagram of a second alternative exemplary high electron-mobility heterostructure 1000 of the present disclosure. The exemplary high electron-mobility heterostructure 1000 comprises a substrate 1001, a doped buffer 1003 on the substrate 1001, a doped charge compensation layer 1005 on the doped buffer 1003, a lower continuously increasing (e.g., monotonically increasing) polarization charge gradient back barrier 1007 on the doped charge compensation layer 1005, an upper continuously decreasing (e.g., monotonically decreasing) polarization charge gradient back barrier 1009 on the lower continuous gradient back barrier 1007, an unintentionally doped (UID) channel 1011 on the upper continuous gradient back barrier 1009, and a charge generation layer 1013 on the UID channel 1011. Optionally, there may be at least one of the following: a nucleation layer 1015 between the substrate 1001 and the doped buffer 1003, at least one intermediate layer 1017 between the UID channel 1011 and the charge generation layer 1013, and at least one capping layer 1019 on the charge generation layer 1013. The lower continuous gradient back barrier 1007, the upper continuous gradient back barrier 1009, at least one intermediate layer 1017, the charge generation layer 1013, and the capping layer 1019 comprise a pseudo-lattice-matched strain layer.

[0024] The substrate 1001 may be silicon (Si), silicon carbide (SiC), sapphire, GaN, AlN, diamond, boron nitride (BN), or any other suitable substrate (e.g., SiC). The doped buffer 1003 may be GaN or AlN, or any other suitable material (e.g., GaN). The doped charge compensation layer 1005 may be GaN.

[0025] The lower continuous gradient back barrier 1007 may be AlGaN with a thickness of more than 3 nm, and the Al percentage in the lower continuous gradient back barrier 1007 is continuously gradientd from the range of 0-5% Al to the range of 2-30% Al (e.g., monotonically increasing). The upper continuous gradient back barrier 1009 may be AlGaN with a thickness of more than 3 nm, and the Al percentage in the upper continuous gradient back barrier 1009 is continuously gradientd from the range of 2-30% Al to the range of 0-5% Al (e.g., monotonically decreasing). That is, the lower continuous gradient back barrier 1007 and the upper continuous gradient back barrier 1009 are gradientd in opposite directions to each other. The lower continuous gradient back barrier 1007 and the upper continuous gradient back barrier 1009 may be gradiented to the same but opposite Al percentages, or to different but opposite Al percentages. The total thickness of the lower continuous gradient back barrier 1007 and the upper continuous gradient back barrier 1009 may be the same or different, and is smaller than the critical thickness for relaxation. In the growth of a pseudo-lattice-matched strain layer, the critical thickness is the thickness beyond which relaxation does not occur, and beyond which relaxation occurs due to misfit dislocation formation.

[0026] The UID channel 1011 may be GaN, AlGaN, or InGaN (e.g., GaN), and may have a thickness in the range of 5 nm to 200 nm. 2DEG can be induced in the UID channel 1011 by the charge generation layer 1013. The charge generation layer 1013 may be AlGaN, ScAlN, InAlN, InGaAlN, or AlN. At least one intermediate layer 1017 may be AlN or GaN. The capping layer 1019 may be GaN, AlN, or SiN. xThis is also acceptable, where x is a positive rational number.

[0027] Figure 11 is a diagram of a third alternative exemplary high electron-mobility heterostructure 1100 of the present disclosure. The exemplary high electron-mobility heterostructure 1100 comprises a substrate 1101, a nucleation layer 1103 on the substrate 1101, a doped buffer 1105 on the nucleation layer 1103, a doped charge compensation layer 1107 on the doped buffer 1105, a lower continuously increasing (e.g., monotonically increasing) polarization charge gradient back barrier 1109 on the doped charge compensation layer 1107, an upper continuously decreasing (e.g., monotonically decreasing) polarization charge gradient back barrier 1111 on the lower continuous gradient back barrier 1109, a UID channel 1113 on the upper continuous gradient back barrier 1111, at least one intermediate layer 1115 on the UID channel 1113, a charge generation layer 1117 on the at least one intermediate layer 1115, and a cap 1119 on the charge generation layer 1117. The lower continuous gradient back barrier 1109, the upper continuous gradient back barrier 1111, at least one intermediate layer 1115, the charge generation layer 1117, and the cap layer 1119 each include a pseudo-lattice matching strain layer.

[0028] The substrate 1101 may be Si, SiC, sapphire, GaN, AlN, diamond, BN, or any other suitable substrate. The doped buffer 1105 may be GaN or AlN, or any other suitable material (e.g., GaN). The doped charge compensation layer 1107 may be beryllium (Be) doped GaN having a thickness of 15 nm. More generally, the doped charge compensation layer 1107 may be doped with Be, magnesium (Mg), iron (Fe), carbon (C), manganese (Mn), or other dopants, thereby allowing band bending to match the quasi-electric field generated near the lower back barrier interface, so that the buffer maintains semi-insulating properties.

[0029] The lower continuous gradient back barrier 1109 may be AlGaN having a thickness greater than 3 nm (e.g., 15 nm), and the Al percentage in the lower continuous gradient back barrier 1109 is continuously gradientd from the range of 0 to 5% Al (e.g., 0%) to the range of 2 to 30% Al (e.g., 10%) (e.g., monotonically increasing). The upper continuous gradient back barrier 1111 may be AlGaN having a thickness greater than 3 nm (e.g., 15 nm), and the Al percentage in the upper continuous gradient back barrier 1111 is continuously gradientd from the range of 2 to 30% Al (e.g., 10%) to the range of 0 to 5% Al (e.g., 0%) (e.g., monotonically decreasing). In other words, the lower continuous gradient back barrier 1109 and the upper continuous gradient back barrier 1111 are gradientd in opposite directions to each other. The lower continuous gradient back barrier 1109 and the upper continuous gradient back barrier 1111 may have the same Al percentage but be gradientd in opposite directions, or different Al percentages but be gradiented in opposite directions. The total thickness of the lower continuous gradient back barrier 1109 and the upper continuous gradient back barrier 1111 may be the same or different, and is smaller than the critical thickness for relaxation. In the growth of a pseudo-lattice-matched strain layer, the critical thickness is the thickness beyond which relaxation does not occur, and beyond which relaxation occurs due to misfit dislocation formation.

[0030] The UID channel 1113 may be GaN, AlGaN, or InGaN, and may have a thickness in the range of 5 nm to 200 nm (e.g., 70 nm GaN). An optional intermediate layer 1115 (e.g., an AlN intermediate layer) may separate the UID channel 1113 from the charge generation layer 1117. 2DEG may be induced in the UID channel 1113 by the charge generation layer 1117. The barrier 1117 may be AlGaN, ScAlN, InAlN, InGaAlN, or AlN (e.g., ScAlN). The capping layer 1119 may be GaN, AlN, or SiN. x It could be (for example, GaN), where x is a positive rational number.

[0031] Figure 12 shows an exemplary method for manufacturing a high electron-mobility heterostructure (e.g., a HEMT or high electron-mobility diode) heterostructure of the present disclosure. Exemplary method 1200 includes forming a substrate in step 1201. Step 1203 of method 1200 includes forming a buffer on the substrate. Step 1205 includes forming a doped charge compensation layer on the buffer. Step 1207 includes forming a double continuous gradient barrier on the doped charge compensation layer. Step 1209 includes forming a channel on the double continuous gradient barrier. Step 1211 includes forming a charge generation layer on the channel.

[0032] While exemplary embodiments of the present disclosure have been described, it will become apparent to those skilled in the art that other embodiments incorporating those concepts can also be used. The embodiments included herein should not be limited to those disclosed, but rather should be limited only by the spirit and scope of the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.

[0033] Elements of different embodiments described herein can be combined to form other embodiments not specifically described above. Various elements described in the context of a single embodiment may be provided separately or in any suitable subordinate combination. Other embodiments not specifically described herein are also within the scope of the following claims.

[0034] Various embodiments of the concepts, systems, devices, structures, and technologies seeking protection are described herein with reference to the relevant drawings. Alternative embodiments can be contemplated without departing from the scope of the concepts, systems, devices, structures, and technologies described herein.

[0035] Note that in the above description and drawings, various connections and positional relationships (e.g., above, below, adjacent, etc.) are described between elements. Unless otherwise specified, these connections and / or positional relationships may be direct or indirect, and the described concepts, systems, devices, structures, and technologies are not intended to be limited in this respect. Therefore, the connection of entities may refer to a direct or indirect connection, and the positional relationship between entities may be a direct or indirect positional relationship.

[0036] As an example of an indirect positional relationship, the reference in this description to forming layer "A" on layer "B" includes situations where one or more intermediate layers (e.g., layer "C") are located between layer "A" and layer "B," provided that the relevant properties and functions of layers "A" and "B" are not substantially altered by the intermediate layer(s). The following definitions and abbreviations shall be used for interpretation of the claims and specification. As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof are intended to cover non-exclusive inclusion. For example, a composition, mixture, process, method, article, or apparatus containing a list of elements is not necessarily limited to these elements and may include other elements not expressly enumerated or other elements specific to such composition, mixture, process, method, article, or apparatus.

[0037] Furthermore, the term “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or design described herein as “exemplary” should not necessarily be construed as being preferable or advantageous to other embodiments or designs. The terms “one or more” and “at least one” are understood to include any integer one or more, i.e., 1, 2, 3, 4, etc. The term “more” is understood to include any integer two or more, i.e., 2, 3, 4, 5, etc. The term “connection” may include indirect “connections” and direct “connections.”

[0038] References in the specification such as "one embodiment," "a certain embodiment," or "an exemplary embodiment" indicate that the described embodiment may include certain features, structures, or characteristics, but any embodiment may include certain features, structures, or characteristics. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when certain features, structures, or characteristics are described in relation to one embodiment, it is considered within the knowledge of a person skilled in the art that such features, structures, or characteristics may be affected in relation to other embodiments, whether or not this is explicitly stated.

[0039] For the purposes of this specification, the terms “top,” “bottom,” “right,” “left,” “vertical,” “horizontal,” “top,” and “bottom,” and their derivatives, to give a few examples, refer to the structures and methods described, as in the orientation of the drawings. The terms “overlying,” “atop,” “on top,” “positioned on,” or “positioned atop” mean that a first element, such as a first structure, is located on a second element, such as a second structure, and that an intervening element, such as an interface structure, may be located between the first and second elements. The term “direct contact” means that a first element, such as a first structure, and a second element, such as a second structure, are connected without any intervening elements. Such terms are sometimes called directional terms or positional terms.

[0040] The use of ordinal numbers such as "first," "second," and "third" in a claim to modify claim elements does not in itself imply priority, precedence, or order of action of one claim element over other claim elements, or a temporal order in which the actions of the method are performed. Rather, it is simply used as a label to distinguish one claim element with a particular name from another element with the same name (other than the use of ordinal numbers).

[0041] The terms “approximately” and “about” may be used in some embodiments to mean within ±20% of the target value, within ±10% of the target value, within ±5% of the target value, and within ±2% of the target value. The terms “approximately” and “about” may include the target value. The term “substantially equal” may be used in some embodiments to mean values ​​within ±20% of each other, within ±10% of each other, within ±5% of each other, and within ±2% of each other.

[0042] The term “substantially” may be used in some embodiments to refer to a value within ±20%, ±10%, ±5%, and ±2% of a comparative measurement. For example, a first direction that is “substantially” perpendicular to a second direction may refer to a first direction that is within ±20% of a 90° angle with the second direction in some embodiments, within ±10% of a 90° angle with the second direction in some embodiments, within ±5% of a 90° angle with the second direction in some embodiments, and within ±2% of a 90° angle with the second direction in some embodiments.

[0043] It should be understood that the subject matter of the disclosure is not limited in its application to the configuration details and arrangement of components described or shown in the following description or drawings. Other embodiments of the subject matter of the disclosure are possible and can be practiced and implemented in a variety of ways.

[0044] Furthermore, it should be understood that the expressions and terminology used herein are for illustrative purposes only and should not be considered limiting. Accordingly, those skilled in the art will understand that the underlying concepts of this disclosure can be readily used as a basis for designing other structures, methods, and systems to accomplish some of the objectives of the disclosed subject matter. Accordingly, the claims should be deemed to include such equivalent configurations, as long as they do not deviate from the spirit and scope of the disclosed subject matter.

[0045] While the disclosed subject matter is described and illustrated in the exemplary embodiments described above, it should be understood that this disclosure is illustrative only and numerous modifications may be made to the details of the implementation of the disclosed subject matter without departing from the spirit and scope of the disclosed subject matter.

Claims

1. A high electron mobility heterostructure, circuit board and The buffer on the aforementioned substrate, The doped charge compensation layer on the buffer, A double continuous gradient barrier on the doped charge compensation layer having increasing and decreasing polarization charges, The channel on the double continuous gradient barrier, A high electron-mobility heterostructure comprising a charge generation layer on the channel.

2. The high electron mobility heterostructure according to claim 1, wherein the substrate is one of silicon (Si), silicon carbide (SiC), sapphire, gallium nitride (GaN), aluminum nitride (AlN), boron nitride (BN), and diamond.

3. The high electron mobility heterostructure according to claim 1, wherein the buffer is one of gallium nitride (GaN) and aluminum nitride (AlN).

4. The high electron mobility heterostructure according to claim 1, wherein the doped charge compensation layer is gallium nitride (GaN) doped with at least one of beryllium, magnesium, iron, carbon, and manganese.

5. The aforementioned double continuous gradient barrier, A first aluminum gallium nitride (AlGaN) barrier layer having a monotonically increasing polarization charge and an aluminum (Al) content gradiented from a first range of 0% to 5% to a second range of 2% to 30%, The high electron mobility heterostructure according to claim 1, comprising: a second AlGaN barrier layer on the first AlGaN barrier layer having a gradient aluminum (Al) content from a first range of 2% to 30% to a second range of 0% to 5%, having a monotonically decreasing polarization charge.

6. The first range of the first AlGaN barrier layer includes one of the following: the same as the second range of the second AlGaN barrier layer, and different from the second range of the second AlGaN barrier layer. The high electron mobility heterostructure according to claim 5, wherein the second range of the first AlGaN barrier layer is the same as the first range of the second AlGaN barrier layer, and different from the first range of the second AlGaN barrier layer.

7. The high electron mobility heterostructure according to claim 5, wherein the first AlGaN barrier layer has a thickness of more than 3 nm, the second AlGaN barrier layer has a thickness of more than 3 nm, the thickness of the first barrier layer is one of the following: the same as the thickness of the second barrier layer, and a different thickness, and the combined thickness of the first AlGaN barrier layer and the second AlGaN barrier layer is less than the critical thickness for relaxation.

8. The high electron mobility heterostructure according to claim 1, wherein the channel is an unintentionally doped channel which is one of gallium nitride (GaN) and indium gallium nitride (InGaN).

9. The high electron mobility heterostructure according to claim 1, wherein the charge generation layer is one of aluminum gallium nitride (AlGaN), scandium aluminum nitride (ScAlN), indium aluminum nitride (InAlN), indium aluminum gallium nitride (InAlGaN), and aluminum nitride (AlN).

10. The nucleation layer between the substrate and the buffer, At least one intermediate layer between the channel and the charge generation layer, A capping layer on the charge generation layer, wherein the at least one intermediate layer is one of aluminum nitride (AlN) and gallium nitride (GaN), and the capping layer is made of GaN, AlN, and silicon nitride (SiN) ｘ The high electron mobility heterostructure according to claim 1, further comprising: a capping layer, which is one of the following, where x is a positive rational number;

11. A method for producing a high electron mobility heterostructure, Forming a substrate, Forming a buffer on the aforementioned substrate, Forming a doped charge compensation layer on the buffer, To form a double continuous gradient barrier on the doped charge compensation layer having increasing and decreasing polarization charges, Forming a channel on the double continuous gradient barrier, A method comprising forming a charge generation layer on the channel.

12. The method according to claim 11, wherein the substrate is one of silicon (Si), silicon carbide (SiC), sapphire, gallium nitride (GaN), aluminum nitride (AlN), boron nitride (BN), and diamond.

13. The method according to claim 11, wherein the buffer is one of gallium nitride (GaN) and aluminum nitride (AlN).

14. The method according to claim 11, wherein the doped charge compensation layer is gallium nitride (GaN) doped with at least one of beryllium, magnesium, iron, carbon, and manganese.

15. The aforementioned double continuous gradient barrier, A first aluminum gallium nitride (AlGaN) barrier layer having a monotonically increasing polarization charge and an aluminum (Al) content gradiented from a first range of 0% to 5% to a second range of 2% to 30%, The method according to claim 11, comprising: a second AlGaN barrier layer on the first AlGaN barrier layer having an aluminum (Al) content graded from a first range of 2% to 30% to a second range of 0% to 5%, having a monotonically decreasing polarization charge.

16. The first range of the first AlGaN barrier layer includes one of the following: the same as the second range of the second AlGaN barrier layer, and different from the second range of the second AlGaN barrier layer. The method according to claim 15, wherein the second range of the first AlGaN barrier layer is the same as the first range of the second AlGaN barrier layer, and different from the first range of the second AlGaN barrier layer.

17. The method according to claim 15, wherein the first AlGaN barrier layer has a thickness of more than 3 nm, the second AlGaN barrier layer has a thickness of more than 3 nm, the thickness of the first barrier layer is one of the following: the same as the thickness of the second barrier layer, and different from the thickness of the first AlGaN barrier layer and the second AlGaN barrier layer combined has a thickness less than the critical thickness for relaxation.

18. The method according to claim 11, wherein the channel is an unintentionally doped channel which is one of gallium nitride (GaN) and indium gallium nitride (InGaN).

19. The method according to claim 11, wherein the charge generation layer is one of aluminum gallium nitride (AlGaN), scandium aluminum nitride (ScAlN), indium aluminum nitride (InAlN), indium aluminum gallium nitride (InAlGaN), and aluminum nitride (AlN).

20. The nucleation layer between the substrate and the buffer, At least one intermediate layer between the channel and the charge generation layer, A capping layer on the charge generation layer, wherein the at least one intermediate layer is one of aluminum nitride (AlN) and gallium nitride (GaN), and the capping layer is made of GaN, AlN, and silicon nitride (SiN) ｘ The method according to claim 11, further comprising: a capping layer, which is one of the following, where x is a positive rational number;

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