Decomposition Mechanisms of Di-tert-butylaminoarsane (DTBAA)

Abstract

III–V semiconductors containing small amounts of nitrogen (“dilute nitrides”) are very promising material systems for optoelectronic applications. Devices based on dilute nitrides currently suffer from problematic C incorporation. To overcome this problem, a novel nitrogen (N) and arsenic (As) precursor for metal–organic vapor phase epitaxy (MOVPE) of the dilute nitride di-tert-butylaminoarsane (DTBAA) has been introduced. DTBAA in comparison to the commonly used 1,1-dimethylhydrazine (UDMHy) showed a significantly improved N incorporation efficiency. The molecule exhibits no strong carbon (C)–N bond, and the C is only present in large alkyl groups which form fewer C radicals since β-H elimination is the dominating decomposition process. This should significantly lower the problematic C incorporation in dilute nitrides and lead to highly efficient devices. To understand the high N incorporation efficiency as well as the As incorporation, the gas-phase decomposition of this novel precursor has been studied with a real time Fourier transform (FT) quadrupole ion trap mass spectrometer (iTrap) from Carl Zeiss SMT GmbH in a horizontal Aixtron Aix 200 GFR MOVPE reactor. Formation of isobutane and isobutene proves a radical cleavage and β-H-elimination as decomposition processes of the tert-butyl groups attached to the molecule. Furthermore, the appearance of ammonia (NH3) has been detected. This indicates a direct cleavage of the As–N bond of the molecule, resulting in the formation of an aminyl radical (NH2•). The formation of NH2• explains the high N incorporation efficiency of DTBAA as well as its limitations due to desorption of NH3 at higher temperatures.