HYDROGEN IN CRYSTALLINE SEMICONDUCTORS .2. III-V COMPOUNDS

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, Al(x) 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 less-than-or-equal-to 400-degrees-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 H-2, 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.