Growth and Characterization of (La,Sr)(Al,Ta)O3 Single Crystals: a Promising Substrate for GaN Epitaxial Growth

Abstract

Experimental results on the growth and characterization of single crystals of mixed perovskite (La,Sr)(Al,Ta)O3 (LSAT), a promising material to prepare substrates for GaN epitaxial layers, growth by the Czochralski method, are reported. The single crystals obtained along <111> orientation up to 20 mm in diameter and 50 mm in length were free of inclusions and macroscopic defects. The optical transmission was measured in the region 200 nm – 3000 nm. For the of <111> oriented LSAT single crystals, its measured unit cell parameter (a = 7.730 Å) matches well to the GaN lattice. The chemical composition was checked by electron microprobe analysis. It was found that it is close to the stoichiometric one. With Lang transmission topography growth striations and dislocations were examined. Data on Vickers microhardness, thermal expansion coefficient, etch pit density and temperature dependence of electrical conductivity and capacitance are reported.

Effect of target–substrate distance on the quality of AlN films grown on Si(110) substrates by pulsed laser deposition

“…Nevertheless, the lattice parameter and coefficient of thermal expansion (CTE) mismatches between AlN and Si(111) are as large as 27% and 49%, respectively, which would cause high-density defects in as-grown AlN films [4]. Additionally, AlN films grown by MOCVD or magnetron sputtering (MS) usually exhibit thick interfacial layer, poor surface morphology owing to serious interfacial reactions between films and substrates at high temperature, which greatly deteriorates the performance of electronic devices [3][4][5][6][7]. To solve these problems, AlN films grown on Si(110) substrates by pulsed laser deposition (PLD) have been deployed.…”

Synthesis of high-quality AlN films on (La,Sr) (Al,Ta)O3 substrates by pulsed laser deposition

“…The LSAT crystals were grown by the conventional Czochralski method [8,10] [10]. The as-grown LSAT crystals were polished by diamond slurries followed by a chemical mechanical polishing process to achieve flat surfaces [10], and the LSAT substrates with the size of 1 Â 1 cm 2 were bought from Hefei Kejing Materials Technology Co., Ltd.…”

“…The as-grown LSAT crystals were polished by diamond slurries followed by a chemical mechanical polishing process to achieve flat surfaces [10], and the LSAT substrates with the size of 1 Â 1 cm 2 were bought from Hefei Kejing Materials Technology Co., Ltd. The as-received LSAT(1 1 1) substrates were cleaned by acetone and deionized water in turn, and then transferred into an ultra-high vacuum-PLD growth chamber with a background pressure of 2.0 Â 10 À 10 Torr.…”

Growth of oxide compounds under dynamic atmosphere composition

“…In this case, 5N nitrogen with total pressure p = 1 bar can be described as a constant admixture of ≈ 2 × 10 −6 bar O 2 in nitrogen. p O2 = 2 × 10 −6 bar is too high for the growth of (La,Sr)(Al,Ta)O 3 (LSAT) crystals that are dark-red colored in the as-grown state and can be bleached by annealing in H 2 [9]. Other oxides are unstable at elevated T under too low p O2 , and typically minor amounts of oxygen are added to the gas: La 1−x Nd x GaO 3 from N 2 + 1% O 2 [10]; Sm 3 Ga 5 O 12 or Gd 3 Ga 5 O 12 from N 2 with 0.9 or 1.5% O 2 , respectively [11].…”