Shallow donors and D-X centers neutralization by atomic hydrogen in GaAlAs doped with silicon.

Hydrogen plasma exposure of silicon doped Gal-xAlxAs epilayers with x 0.37 causes a strong reduction of the free electron concentration in the layers. For x 0.29, this effect is accompanied by a simultaneous increase of the electron mobility. This is interpreted, as in GaAs, in terms of a neutralization of the active silicon donors by atomic hydrogen. The neutralization efficiency of the shallow donnors increases as x increases. For x~-0.25, the D-X centers are very efficiently neutralized by hydrogen and, as a consequence, the conductivity mechanisms after exposure are only governed by the remaining shallow donors. For 0.29 x 0.37, most of the D-X centers are neutralized but the electron mobility after hydrogenation is reduced.