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CN-122002875-A - Novel ScAlN semiconductor material with extremely high hole mobility, and preparation method and application thereof

CN122002875ACN 122002875 ACN122002875 ACN 122002875ACN-122002875-A

Abstract

A novel ScAlN semiconductor material with extremely high hole mobility, a preparation method and application thereof are provided, the material has a ScAlN digital alloy structure, the material is formed by periodically and alternately stacking basic repeating units (ScN) m /(AlN) n along an epitaxial growth direction, wherein (ScN) m represents ScN of m atomic layers, (AlN) n represents AlN of n atomic layers, m has a value of 3 or 5, n has a value of 1, the number of repeating cycles of the basic repeating units is x, and x is a natural number greater than or equal to 1. The structure utilizes unique octahedral coordination tendency of Sc atoms, local symmetry break and hybridization orbit reconstruction are induced in the lattice by periodically introducing and limiting the number and the sequence of ScN layers in an AlN lattice, the electron state distribution of valence band tops is remodelled while a wide band gap is kept, and the hole mobility is improved.

Inventors

  • ZHU JIADUO
  • FU LIUYING
  • JI JIAWEI
  • ZHANG JINCHENG
  • WANG XINHAO
  • ZHANG TAO
  • ZHANG YACHAO
  • XU CHENGRUI
  • HAO YUE

Assignees

  • 西安电子科技大学

Dates

Publication Date
20260508
Application Date
20260210

Claims (8)

  1. 1. A novel ScAlN semiconductor material with extremely high hole mobility is characterized by having a ScAlN digital alloy structure, wherein the lattice structure of the material is formed by periodically and alternately stacking basic repeating units (ScNs) m /(AlN) n along the epitaxial growth direction, wherein (ScNs) m represents ScNs of m atomic layers, (AlNs) n represents AlNs of n atomic layers, the value of m is 3 or 5, the value of n is 1, the number of the repeating cycles of the basic repeating units is x, and x is a natural number greater than or equal to 1.
  2. 2. The novel ScAlN semiconductor material according to claim 1, wherein the ScAlN semiconductor material is prepared by an MOCVD process, and the specific process comprises the steps of keeping ammonia continuously fed in a pulse growth mode of periodically switching a specific MO source, (1) a ScN sub-layer growth stage of starting a Sc source, closing an Al source and growing a ScN of 3 or 5ML, (2) an AlN sub-layer growth stage of starting an Al source and growing an AlN of 1 ML, and performing the steps (1) and (2) circularly until a preset total thickness is achieved.
  3. 3. A MOSFET device with an enhanced p-channel vertical trench gate structure is characterized by sequentially comprising a drain electrode (8), a p-type GaN substrate (1) and a p-type GaN drift layer (2) which are arranged in a stacked mode from bottom to top, wherein an n-type channel layer (3), a p-type GaN heavily doped layer (4) and a source electrode (7) are sequentially arranged on the tops of two sides of the p-type GaN drift layer (2) in a stacked mode, a vertical trench structure is formed in the p-type GaN drift layer (2), the n-type channel layer (3) and the p-type GaN heavily doped layer (4), al 2 O 3 gate dielectric layers (5) are covered on the side walls and the bottoms of the vertical trench structure, a gate electrode (6) positioned on the inner side of the Al 2 O 3 gate dielectric layers (5) is arranged in the vertical trench structure, and the n-type channel layer (3) is made of ScAlN semiconductor material (ScN) 3 /(AlN) 1 or (ScN) 5 /(AlN) 1 ) according to claim 1 or 2.
  4. 4. The MOSFET device according to claim 3, wherein the p-type GaN drift layer (2) has a doping concentration of 1X 10 16 -5×10 16 cm -3 and a thickness of 300-800: 800 nm, the n-type channel layer (3) has a doping concentration of 1X 10 15 -5×10 15 cm -3 and a thickness of 100-200: 200 nm, the p-type GaN heavily doped layer (4) has a doping concentration of 1X 10 19 -5×10 19 cm -3 and a thickness of 200-300: 300 nm, the Al 2 O 3 gate dielectric layer (5) is made of Al 2 O 3 and a thickness of 20-30: 30 nm, and the gate electrode (6) is made of metal W and has a thickness of 280-470: 470 nm.
  5. 5. The preparation method of the MOSFET device with the enhanced p-channel vertical trench gate structure is characterized by comprising the following steps of: Step 1, a lightly doped P-type GaN drift layer (2) with the thickness of 300-800 nm is grown on a heavily doped P-type GaN substrate (1) by using an MOCVD process; Step 2, growing a lightly doped n-type channel layer (3) on a p-type GaN drift layer (2) by using an MOCVD process, adopting a pulse growth mode of periodically switching a specific MO source, keeping ammonia continuously introduced, (1) a ScN sub-layer growth stage, namely, starting an Sc source, closing an Al source and growing 3 or 5 ML ScN, (2) an AlN sub-layer growth stage, namely, starting the Sc source, starting the Al source and growing 1ML AlN, and circularly executing the steps (1) and (2) until the total thickness of the n-type channel layer (3) reaches 100-200 nm; Step 3, growing a p-type GaN heavily doped layer (4) with the thickness of 200-300 nm on the n-type channel layer (3) by using an MOCVD process; Defining a grid groove plane pattern on the p-type GaN heavily doped layer (4) by using a photoetching process, and etching by using a plasma reaction ion etching process until the p-type GaN drift layer (2) is exposed to form a grid groove; Uniformly depositing an Al 2 O 3 dielectric layer (5) with the thickness of 20-30 nm a on the inner wall of the grid electrode groove by using an atomic layer deposition technology; Step 6, depositing metal W by using a CVD process to completely fill the gate trench, and forming a gate electrode (6) with the thickness of 280-470 nm a; and 7, depositing a Ni/Au metal lamination by utilizing electron beam evaporation on the p-type GaN heavily doped layer (4) to form a source electrode (7), and depositing the Ni/Au metal lamination by utilizing electron beam evaporation on the back surface of the p-type GaN substrate (1) to form a drain electrode (8).
  6. 6. A p-type GaN power diode device based on an AlN substrate is characterized by comprising an n-region electrode (14), an n-type AlN substrate (9), an n-type AlGaN drift layer (10), a p-type hole transport layer (11), a p-type AlGaN hole injection layer (12) and a p-region electrode (13) which are arranged in a stacked mode from bottom to top, wherein the p-type hole transport layer (11) is made of the ScAlN semiconductor material according to claim 1 or 2, namely (ScN) 3 /(AlN) 1 or (ScN) 5 /(AlN) 1 .
  7. 7. The p-type GaN power diode device according to claim 6, wherein the doping concentration of the n-type AlGaN drift layer (10) is 1×10 16 -5×10 16 cm -3 and the thickness is 5-10 um, the doping concentration of the p-type hole transport layer (11) is 1×10 15 -5×10 15 cm -3 and the thickness is 100-200 nm, and the doping concentration of the p-type AlGaN hole injection layer (12) is 1×10 19 -5×10 19 cm -3 and the thickness is 200-300 nm.
  8. 8. The preparation method of the p-type GaN power diode device based on the AlN substrate is characterized by comprising the following steps of: step 1, a lightly doped p-type AlGaN drift layer (10) with the thickness of 5-10 um ℃ is grown on a heavily doped n-type AlN substrate (9) by using an MOCVD process; Step 2, growing a lightly doped p-type hole transport layer (11) on a p-type AlGaN drift layer (10) by using an MOCVD process, adopting a pulse growth mode of periodically switching a specific MO source, keeping ammonia continuously introduced, (1) a ScN sub-layer growth stage, namely, starting the Sc source, closing an Al source and growing 3 or 5ML ScN, (2) an AlN sub-layer growth stage, namely, starting the Sc source, starting the Al source and growing 1 ML AlN, and circularly executing the steps (1) and (2) until the total thickness of the p-type hole transport layer (11) reaches 100-200 nm; step 3, growing a heavily doped p-type AlGaN hole injection layer (12) with the thickness of 200-300 nm a on the p-type hole transport layer (11) by using an MOCVD process; And 4, depositing a Ni/Au metal lamination by utilizing electron beam evaporation on the p-type AlGaN hole injection layer (12), annealing to form a p-region electrode (13), depositing a Ti/Al/Ni/Au metal lamination by utilizing electron beam evaporation on the back surface of the n-type AlN substrate (9), and annealing to form an n-region electrode (14).

Description

Novel ScAlN semiconductor material with extremely high hole mobility, and preparation method and application thereof Technical Field The invention belongs to the technical field of semiconductor material preparation, and particularly relates to a novel ScAlN semiconductor material with extremely high hole mobility, and a preparation method and application thereof. Background Nitride semiconductors are used as the representatives of the third-generation semiconductor materials, and play a decisive role in supporting and pushing in the fields of photoelectricity, radio frequency, power electronics and the like by virtue of excellent characteristics such as wide forbidden band, high breakdown electric field, high thermal conductivity, high electron saturation drift speed and the like. Carrier mobility is a very important physical parameter in nitride semiconductor materials that directly affects the performance of the material in electronic devices. For example, in high-frequency devices and radio-frequency devices, the improvement of carrier mobility can obviously improve the working frequency of the devices, thereby meeting the requirements of modern integrated circuit industry on high-frequency signal processing, and in power devices, the high mobility is beneficial to reducing conduction loss and switching loss and improving the performance of the whole devices. In general, nitride semiconductors exhibit excellent electron mobility, but their hole mobility is significantly lower, for example, gaN bulk materials typically have electron mobility at room temperature of 1000-1200 cm 2/Vs and hole mobility at room temperature of only 10-20 cm 2/Vs, inN materials with the highest electron mobility in nitrides have electron mobility at room temperature of 3200/cm 2/Vs or higher and hole mobility of less than 30 cm 2/Vs, and current hot-spot semiconductors AlN have hole mobility of less than 10 cm 2/Vs, which makes p-channel nitride electronic devices with holes as carriers generally worse than n-channel devices with electrons as carriers. Under the strong traction of the requirements of p-n complementary power electronic application and digital logic application, how to improve the mobility of p-type carriers and the conductivity of p-type channels has become a core problem in the research and development of nitride semiconductor materials. Particularly, in the case of securing the characteristics of a wide band gap semiconductor, a technique of maintaining high hole mobility is highly competing with patents in industry and academia. For nitride semiconductors such as GaN and AlN, the root cause of low hole mobility mainly comes from N element with strong electronegativity under sp3 hybridization, so that holes tend to be localized, the effective mass of the holes near the top of a valence band is extremely large, and the hole mobility is extremely small. Therefore, how to change the effective mass of holes near the top of the valence band of the nitride semiconductor material by changing the lattice structure and further changing the sp3 hybridization of tetrahedral coordination is a fundamental way to solve the problem of low hole mobility of the nitride. In order to solve the problem of low hole mobility of nitride semiconductors, the currently mainstream technical solutions are mainly divided into the following two aspects: (1) Polarization induces two-dimensional hole gas (2 DHG) generation at GaN/AlGaN（SHAO P, FAN X, LI S, et al. High density polarization-induced 2D hole gas enabled by elevating Al composition in GaN/AlGaN heterostructures[J/OL]. Applied Physics Letters, 2023, 122(14): 142102.） or GaN/AlN（Chaudhuri R, Bader S J, Chen Z, et al. A polarization-induced 2D hole gas in undoped gallium nitride quantum wells[J]. Science, 2019, 365(6460): 1454-1457.） heterojunction interfaces. Group III nitride materials have spontaneous and piezoelectric polarization effects, and due to the discontinuity of polarization at the GaN/AlGaN or GaN/AlN heterojunction interface, negatively charged fixed charges are generated, which attract holes in the valence band in the interface potential well to form a 2DHG for maintaining electroneutrality. The scheme still belongs to an AlN and GaN nitride system, the problem of low mobility caused by large effective mass of holes at the top of a valence band is not solved, and the hole mobility of 2DHG at room temperature 300K is lower than 20cm 2/Vs due to interface scattering introduced by GaN/AlGaN or GaN/AlN heterojunction, so that the hole mobility of a nitride semiconductor is not remarkably improved. (2) The periodic arrangement of atoms in the superlattice structure based on the modulation doping technology （KRISHNA A, RAJ A, HATUI N, et al. Investigation of nitrogen polar p-type doped GaN/AlxGa(1-x)N superlattices for applications in wide-bandgap p-type field effect transistors[J/OL]. Applied Physics Letters, 2019, 115(17): 172105.）. of the GaN/AlGaN superlattice structu