Thermal Activation of Valley-Orbit States of Neutral Magnesium in Silicon

Interstitial magnesium acts as a moderately deep double donor in silicon, and is relatively easily introduced by diffusion. Unlike the case of the chalcogen double donors, parameters of the even-parity valley-orbit excited states 1s(T_2) and 1s(E) have remained elusive. Here we report on further study of these states in neutral magnesium through temperature dependence absorption measurements. The results demonstrate thermal activation from the ground state 1s(A_1) to the valley-orbit states, as observed by transitions from the thermally populated levels to the odd-parity states 2p_0 and 2p_±. Analysis of the data makes it possible to determine the thermal activation energies of transitions from the donor ground state to 1s(T_2) and 1s(E) levels, as well as the binding energies of an electron with the valley-orbit excited states. Keywords: magnesium impurity in silicon, deep center, optical spectroscopy