HYDROGEN IN CRYSTALLINE SEMICONDUCTORS: PART II–III–V COMPOUNDS

Abstract

The properties of hydrogen in III–V semiconductors are reviewed. Atomic hydrogen is found to passivate the electrical activity of shallow donor and acceptor dopants in virtually all III–V materials, including GaAs, Alx Ga1−x As, InP, InGaAs, GaP, InAs, GaSb, InGaP, AlInAs and AlGaAsSb. The passivation is due to the formation of neutral dopant-hydrogen complexes, with hydrogen occupying a bond-centered position in p-type semiconductors and an anti-bonding site in n-type materials. The dopants are reactivated by annealing at ≤400° C. The neutral hydrogen-dopant complexes have characteristic vibrational bands, around 2000cm−1 for stretching modes and 800cm−1 for wagging modes. Deep levels such as EL2, DX and metallic impurities are also passivated by hydrogen. The diffusivity of hydrogen is high in III–V semiconductors and unintentional incorporation can occur during epitaxial growth, annealing in H2, dry etching, water boiling, wet etching or chemical vapor deposition processes, Surface passivation by (NH4)xS or NH3 plasma treatment is also effective in lowering surface recombination velocities in many III-V semiconductors.