Tuesday, December 15, 2015

ALD of III/V compound semiconductor GaAs using novel precursor chemistry from Helsinki

Here is a new ALD process for the III/V compound semiconductor GaAs from Laboratory of Inorganic Chemistry at Helsinki University (Prof. Leskelä & Prof. Ritala). GaAs has a zinc blende crystal structure and is used to manufacture devices such as microwave frequency integrated circuits, monolithic microwave integrated circuits, infrared light-emitting diodes, laser diodes, solar cells and optical windows. So a lot of military technology is based on this material.

Professor Markku Leskelä (on the left) and Professor Mikko Ritala are two of the most well-known names in the world of ALD research. Photo: Peter Herring (http://www.hightechfinland.com/direct.aspx?area=htf&prm1=1058&prm2=article)

However, GaAs is often used as a substrate material for the epitaxial growth of other III-V semiconductors including: Indium gallium arsenide, aluminum gallium arsenide and others that will be become very important channel material for sub 10 nm CMOS for transistors based on vertical and horizontal nano wires. So this paper is sort of back to the roots when ALD was called ALE as in Atomic Layer Epitaxy.

The main author Tiina Sarnet will be defending her Thesis "Non-metal Alkylsilyl Compounds as Precursors in Atomic Layer Deposition of Chalcogenides and Pnictides" on Monday next week, which you can find here:  Download file

Alkylsilyl compounds as enablers of atomic layer deposition: analysis of (Et3Si)3As through the GaAs process

Tiina Sarnet, Timo Hatanpää, Mikko Laitinen, Timo Sajavaara, Kenichiro Mizohat, Mikko Ritala and Markku Leskelä
J. Mater. Chem. C, 2016, Advance Article
DOI: 10.1039/C5TC03079J

A new chemistry has been developed to deposit GaAs, the quintessential compound semiconductor. The ALD process is based on a dechlorosilylation reaction between GaCl3 and (Et3Si)3As. Characteristic ALD growth was demonstrated, indicating good applicability of the alkylsilyl arsenide precursor. ALD of GaAs produced uniform, amorphous and stoichiometric films with low impurity content. This was done with saturating growth rates and an easily controlled film thickness. Crystallization was achieved by annealing. Even though the growth rate strongly decreased with increasing deposition temperature, good quality film growth was demonstrated at 175 to 200 °C, indicating the presence of an ALD window.