Correlated to random transition of ionized impurity distribution in n-type Ge : (As, Ga)

We discuss the broadening of ground-state to bounded excited-state transitions of shallow donors in strongly compensated n-type Ge: (As,Ga) in the presence of electric fields and their gradients, arising from randomly distributed ionized impurities. Quantitative comparison of the experimentally obtained linewidths with Monte Carlo simulation results makes possible, a unique determination of the ionized impurity distribution in the samples. We present clear evidence for the random-to-correlated transition of the ionized impurity distribution as a function of the ionized impurity concentration and of temperature. (C) 2001 Published by Elsevier Science B.V.