Synthesis and Structural and Optical Properties of Ga(As1-xPx)Ge3 and (GaP)yGe5-2y Semiconductors Using Interface-Engineered Group IV Platforms

Patrick M. Wallace, Patrick E. Sims, Chi Xu, Christian D. Poweleit, John Kouvetakis, Jose Menendez

Research output: Contribution to journalArticle

Abstract

Epitaxial synthesis of Ga(As1-xPx)Ge3 alloys on Si(100) substrates is demonstrated using chemical vapor deposition reactions of [D2GaN(CH3)2]2 with P(GeH3)3 and As(GeH3)3 precursors. These compounds are chosen to promote the formation of GaAsGe3 and GaPGe3 building blocks which interlink to produce the desired crystalline product. Ge-rich (GaP)yGe5-2y analogues have also been grown with tunable Ge contents up to 90% by reactions of P(GeH3)3 with [D2GaN(CH3)2]2 under similar deposition protocols. In both cases, the crystal growth utilized Ge1-xSix buffer layers whose lattice constants were specifically tuned as a function of composition to allow perfect lattice matching with the target epilayers. This approach yielded single-phase materials with excellent crystallinity devoid of mismatch-induced dislocations. The lattice parameters of Ga(As1-xPx)Ge3 interpolated among the Ge, GaAs, and GaP end members, corroborating the Rutherford backscattering measurements of the P/As ratio. A small deviation from the Vegard's law that depends on the As/P ratio was observed and corroborated by ab initio calculations. Raman scattering shows evidence for the existence of Ga-As and Ga-P bonds in the Ge matrix. The As-rich samples exhibited photoluminescence with wavelengths similar to those observed for pure GaAsGe3, indicating that the emission profile does not change in any measurable manner by replacing As by P over a broad range up to x = 0.2. Furthermore, the photoluminescence (PL) data suggested a large negative bowing of the band gap as expected on account of a strong valence band localization on the As atoms. Spectroscopic ellipsometry measurements of the dielectric function revealed a distinct direct gap transition that closely matches the PL emission energy. These measurements also showed that the absorption coefficients can be systematically tuned as a function of composition, indicating possible applications of the new materials in optoelectronics, including photovoltaics.

Original languageEnglish (US)
Pages (from-to)35105-35113
Number of pages9
JournalACS Applied Materials and Interfaces
Volume9
Issue number40
DOIs
StatePublished - Oct 11 2017

Keywords

  • gallium arsenide
  • gallium phosphide
  • GeSi buffer layers
  • III'V'IV alloys
  • photoluminescence

ASJC Scopus subject areas

  • Materials Science(all)

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