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

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Abstract
Hydrogen plasma exposure of silicon-doped Ga1−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 donors 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.