New alternative arsenic precursors for the metal-organic vapour-phase epitaxy of III–V semiconductors: in-situ formation of AsH functionality by β elimination of specific metal-organic arsenic compounds

In this study we report on the chemical synthesis, thermal decomposition and first metal-organic vapour-phase epitaxy (MOVPE) growth studies for a new class of metal-organic As compounds, designed as substitutes for the highly toxic AsH3. The key feature of these molecules is the in-situ formation of AsH functions only in the hot temperature zone of thw MOVPE reactor. Compounds with the principal molecular structure As(Rrad)n(Rβ)3−n(n=0, 1, 2; Rrad≡ alkyl group with radical formation, Rβ ≡ alkyl group with β elimination) do not a priori contain the AsH bonds needed for the growth of high quality III–V semiconductors using MOVPE; they are formed in situ in the reactor by thermal decomposition. The postulated β elimination process has been proven by decomposition studies using an ersatz reactor system with quadrupole mass spectrometry for the potential β elimination groups isobutyl and tert-butyl. The principal methods of synthesis of high purity arsenic compounds are presented and discussed. In addition we describe experiments for the MOVPE of GaAs epitaxial layers with the model compound diethyl-tert-butylarsine (DETBAs). The residual impurity levels of GaAs epitaxial layers grown in combination with trimethylgallium for different batches of DETBAs are presented and discussed as a function of the MOVPE growth conditions.