The states, and microscopic diffusion mechanisms, of H in crystalline samples were investigated by using an ab initio molecular dynamics method. The static equilibrium position for neutral H was found to lie around the bond-centered site. Being a negative-U center, the H behaved as a stable donor around the bond-centered site in p-type material, but acted as a stable acceptor around the interstitial site; surrounded by 4 nearest Ga host atoms in n-type material. The H cation diffused along the bond-center → CGa → bond-center → CAs → bond-center path in a high valence electron-density region, with a barrier of 0.46eV, in p-type materials. On the other hand, the H anion diffused along the TGa → Hex → TAs → Hex → TGa path in a low electron-density region, with a barrier of 0.55eV, in n-type material. The diffusion was more effective in p-type samples. Good agreement with experiment was found.

Amphoteric charge states and diffusion barriers of H in GaAs C.Wang, Q.M.Zhang: Physical Review B, 1999, 59[7], 4864-8