Fabrication and characterization of transparent conductive Sn‐doped β‐Ga₂O₃ single crystal

Abstract

PACS 72.80. Jc, 78.66.Li, 81.10.Fq Transparent conductive Sn-doped β-Ga 2 O 3 single crystal with high crystallinity was successfully fabricated as a substrate for the growth of GaN-based compounds. Sn-doped β-Ga 2 O 3 single crystals were grown using a floating zone (FZ) method, and the properties of electrical conductivity, optical transmittance, and crystallinity were characterized to optimize the growth condition. It was found that these properties are controlled by the Sn doping concentration, and the specimen for 32 ppm Sn-doped β-Ga 2 O 3 single crystal was optimized to satisfy these properties simultaneously, i.e. the substrate with the internal optical transmittance of above ~85 % in the visible region, the electrical resistivity of 4.27×10 -2 Ωcm, the carrier density of 2.26×10 18 cm -3 , and the FWHM of X-ray rocking curve of 43 arcsec was obtained.

Growth and characterization of α-, β-, and ϵ-phases of Ga2O3 using MOCVD and HVPE techniques

“…Of the four distinct polymorphs, most research has focused on the monoclinic β-phase, which is the only thermodynamically stable phase from room temperature to its melting point at ∼ 1800 • C; all other polymorphs are metastable and have been reported to transform into the β-phase within the temperature range of 750-950 • C [6]. Single-crystal substrates of β-Ga 2 O 3 are grown by a variety of melt-based methods, including CONTACT Lisa M. Porter lporter@andrew.cmu.edu floating-zone (FZ) [7][8][9][10], edge-defined film-fed growth (EFG) [11], and Czochralski (CZ) [12,13] methods. Epitaxial films of β-Ga 2 O 3 have been grown using various vapor phase techniques, including metalorganic chemical vapor deposition (MOCVD) [14], molecular beam epitaxy (MBE) [1,[15][16][17][18][19], pulsed-laser deposition (PLD) [20], halide vapor phase epitaxy (HVPE) [21], and MIST epitaxy [22].…”

Dopant activation in Sn-doped Ga2O3 investigated by X-ray absorption spectroscopy

“…With an electron affinity of 3.7 eV, 1 bandgap of 4.8 eV 2 and transmissivity above 80% in the wavelength range of 300 to 1000 nm, 3 Ga2O3 appears to be an excellent candidate wide-bandgap TCO with low electron affinity. Ga2O3 can be doped with tin, achieving donor concentrations above 10 19 cm -3 when grown in bulk-crystal form 3 and above 10 18 cm -3 when deposited by molecular-beam epitaxy (MBE) in the 540 to 600°C range. 4 However, thin films deposited using atomic-layer deposition (ALD) and pulsed-laser deposition (PLD) at more moderate temperatures in the 100 to 200°C range have not exhibited high Sn dopant activation;…”

Corundum‐structured α‐phase Ga2O3‐Cr2O3‐Fe2O3 alloy system for novel functions

“…Ga 2 O 3 has five types of crystal structures, α-, β-, γ-, δ-, ε- [8], and β-Ga 2 O 3 is recognized as the most stable phase. β-Ga 2 O 3 is a promising material as a wide band gap semiconductor as demonstrated by highly crystalline bulk substrates commercially available [9][10][11], highly sensitive deep ultraviolet sensors [12,13], and atomically flat epilayers with the step-flow growth by molecular beam epitaxy [14,15]. On the other hand, it has been generally difficult to obtain highly crystalline α-Ga 2 O 3 .…”