Investigation of the growth technique dependence on the optical properties of Si_1-xGe_x alloy layers

The discrepancy between the measured photoluminescence spectra of Si_1-xGe_x strained alloy layers originating from molecular beam epitaxy (MBE) and chemical vapor deposition (CVD) processes is investigated. Sharp excitonic band edge luminescences are observed for films by both growth techniques. For certain films grown by MBE, the photoluminescence spectra contain an additional broad alloy band luminescence at low energy. Deuterium passivation of the MBE layers is shown to annihilate the broad band luminescence and to increase the band edge luminescence intensity. These results are compared with the more intense band edge luminescence signals from CVD layers for which abundant hydrogen radicals are usually present during the deposition.