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Electronic and optical properties of ultrawide bandgap perovskite semiconductors via first principles calculations

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2020-12-07
JournalApplied Physics Letters
AuthorsRadi A. Jishi, Robert J. Appleton, David M. Guzman, Radi A. Jishi, Robert J. Appleton
InstitutionsCalifornia State University Los Angeles, Purdue University West Lafayette
Citations20
AnalysisFull AI Review Included

Technical Documentation & Analysis: Ultrawide Bandgap Perovskites vs. MPCVD Diamond

Section titled “Technical Documentation & Analysis: Ultrawide Bandgap Perovskites vs. MPCVD Diamond”

This document analyzes the research on novel Ultrawide Bandgap (UWBG) perovskite semiconductors, positioning 6CCVD’s high-performance MPCVD diamond materials as the superior benchmark and integration platform for next-generation high-power and deep-UV optoelectronic applications.

Executive Summary

Section titled “Executive Summary”
  • Novel UWBG Materials: First-principles calculations confirm three barium-based perovskites (BaZrO3, Ba2CaTeO6, Ba2K2Te2O9) as novel UWBG semiconductors, exhibiting bandgaps between 4.65 eV and 5.24 eV.
  • Deep-UV Relevance: These materials show significant absorption in the deep-UV region, making them candidates for advanced optoelectronic devices, a market traditionally dominated by diamond and GaN.
  • Direct Bandgap Advantage: Ba2CaTeO6 (5.24 eV) and Ba2K2Te2O9 (4.65 eV) exhibit direct bandgaps, which is favorable for efficient light emission/absorption compared to the indirect bandgap of BaZrO3.
  • Critical Doping Challenge: A major limitation identified is the strong tendency for hole self-trapping (EST ~0.25 eV) near oxygen atoms, which severely impedes the achievement of stable p-type conductivity via traditional chemical doping.
  • Diamond Benchmark: The research explicitly compares these novel materials to established UWBG platforms, including MPCVD diamond (5.5 eV), which retains the highest intrinsic bandgap and superior thermal properties.
  • 6CCVD Value Proposition: 6CCVD offers the necessary high-purity Single Crystal Diamond (SCD) substrates and highly stable, controllable Boron-Doped Diamond (BDD) films to overcome the p-doping challenges faced by these new oxide materials in heterostructure integration.

Technical Specifications

Section titled “Technical Specifications”

The following hard data points were extracted from the first-principles calculations using the HSE06 hybrid functional potential:

ParameterValueUnitContext
UWBG Semiconductor Definition> 3.4eVBandgap greater than GaN
BaZrO3 Bandgap (HSE06)4.90eVIndirect transition
Ba2CaTeO6 Bandgap (HSE06)5.24eVDirect transition
Ba2K2Te2O9 Bandgap (HSE06)4.65eVDirect transition
BaZrO3 Hole Self-Trapping Energy (EST)0.247eVEnergy stabilized by lattice distortion
Ba2CaTeO6 Hole Self-Trapping Energy (EST)0.256eVEnergy stabilized by lattice distortion
Ba2K2Te2O9 Hole Self-Trapping Energy (EST)0.248eVEnergy stabilized by lattice distortion
BaZrO3 Lattice Constant (a)4.19ÅIdeal Perovskite (Pm3m)
Ba2CaTeO6 Lattice Constant (a)8.3536ÅDouble Perovskite (Fm3m)
Ba2K2Te2O9 Lattice Constants (a, c)6.047, 16.479ÅTriple Perovskite (P63/mmc)

Key Methodologies

Section titled “Key Methodologies”

The electronic and optical properties were determined using advanced computational techniques, primarily Density Functional Theory (DFT) with hybrid functionals.

  1. Computational Framework: Calculations utilized the hybrid-functional HSE06 potential (Heyd-Scuseria-Ernzerhof) to accurately predict bandgaps, which are often underestimated by standard PBE functionals (e.g., PBE predicted BaZrO3 bandgap at 2.94 eV vs. HSE06 at 4.90 eV).
  2. Code Implementation: Electronic structure and optical properties were calculated using the all-electron, full potential, linear augmented plane wave method (WIEN2k code). Hole trapping calculations were performed using the VASP code.
  3. Wave Function Cutoff: The wave function expansion utilized a cutoff parameter RmtKmax = 7, where Rmt is the smallest muffin-tin radius.
  4. Charge Density Expansion: Charge density was Fourier expanded up to Gmax = 12 Ry1/2.
  5. Energy Cutoff: A kinetic energy cutoff of 400 eV was applied for all hole trapping calculations.
  6. Supercell Structures for Polaron Study: Optimized supercells were used to model small polarons and hole self-trapping:
    • BaZrO3: 3x3x3 supercell (135 atoms).
    • Ba2CaTeO6: 80 atom supercell (doubled conventional unit cell).
    • Ba2K2Te2O9: 2x2x1 supercell (120 atoms).

6CCVD Solutions & Capabilities

Section titled “6CCVD Solutions & Capabilities”

This research confirms the intense global focus on UWBG materials for high-power and deep-UV applications. While novel perovskites show promise, they face significant electronic challenges (p-doping difficulty) where MPCVD diamond provides established, superior performance and integration solutions.

Research Requirement / Challenge6CCVD Diamond SolutionTechnical Advantage & Sales Driver
UWBG Performance BenchmarkOptical Grade Single Crystal Diamond (SCD)Diamond (5.5 eV bandgap) offers the highest intrinsic bandgap, ensuring maximum performance in deep-UV and high-field environments. Its thermal conductivity (> 2000 W/mK) is orders of magnitude higher than any oxide, critical for high-power RF-electronics.
Deep-UV Optoelectronics SubstratesHigh Purity SCD Plates6CCVD SCD is transparent down to 225 nm, making it the ideal window, lens, or substrate material for deep-UV emitters and detectors, minimizing parasitic absorption losses.
P-Type Doping SolutionHeavy Boron-Doped Diamond (BDD)The perovskites suffer from hole self-trapping (EST ~0.25 eV), making p-doping unstable. 6CCVD BDD provides a stable, highly conductive p-type layer, essential for creating reliable ohmic contacts or p-n junctions in heterostructures with UWBG oxides.
Custom Substrate DimensionsCustom SCD/PCD Wafers up to 125mmFor scaling up research prototypes, 6CCVD provides large-area Polycrystalline Diamond (PCD) up to 125mm and custom-sized SCD plates, supporting advanced epitaxial growth of novel UWBG films.
Surface Quality for EpitaxyUltra-Polished SCD/PCDWe guarantee surface roughness (Ra) < 1 nm for SCD and Ra < 5 nm for inch-size PCD, ensuring the high-quality interface required for integrating perovskite films (e.g., BaZrO3) onto diamond platforms.
Device Integration & ContactingCustom Metalization Services6CCVD offers in-house deposition of standard and custom metal stacks (Au, Pt, Pd, Ti, W, Cu) directly onto diamond surfaces, simplifying the fabrication of high-performance UWBG devices and contacts.

Engineering Support

Section titled “Engineering Support”

6CCVD’s in-house PhD engineering team specializes in the electronic and optical properties of UWBG materials. We can assist researchers and engineers in selecting the optimal diamond material (SCD, PCD, or BDD) and surface preparation necessary to replicate or extend this research into functional high-power and deep-UV optoelectronic devices.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Recent research in ultrawide-bandgap (UWBG) semiconductors has focused on traditional materials such as Ga2O3, AlGaN, AlN, cubic BN, and diamond; however, some materials exhibiting a single perovskite structure have been known to yield bandgaps above 3.4 eV, such as BaZrO3. In this work, we propose two materials to be added to the family of UWBG semiconductors: Ba2CaTeO6 exhibiting a double perovskite structure and Ba2K2Te2O9 with a triple perovskite structure. Using first-principles hybrid functional calculations, we predict the bandgaps of all the studied systems to be above 4.5 eV, with strong optical absorption in the ultraviolet region. Furthermore, we show that holes have a tendency to get trapped through lattice distortions in the vicinity of oxygen atoms, with an average trapping energy of 0.25 eV, potentially preventing the enhancement of p-type conductivity through traditional chemical doping.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2001 - Nobel Lecture: Quasielectric fields and band offsets: Teaching electrons new tricks [Crossref]
  2. 2015 - The blue LED Nobel Prize: Historical context, current scientific understanding, human benefit [Crossref]
  3. 2013 - History of gallium-nitride-based light-emitting diodes for illumination [Crossref]
  4. 2011 - Solid-state lighting: ‘The case’ 10 years after and future prospects [Crossref]
  5. 2018 - Ultrawide-bandgap semiconductors: Research opportunities and challenges [Crossref]
  6. 1982 - Semiconductors for high-voltage, vertical channel field-effect transistors [Crossref]
  7. 1965 - Physical limitations on frequency and power parameters of transistors [Crossref]
  8. 2012 - Role of self-trapping in luminescence and p-type conductivity of wide-band-gap oxides [Crossref]
  9. 2018 - Self-trapped holes in BaTiO3 [Crossref]
  10. 2019 - Enhanced doping efficiency of ultrawide band gap semiconductors by metal-semiconductor junction assisted epitaxy [Crossref]

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