Influence of the mesa size on Ge island electroluminescence properties

The influence of the mesa size on the structural and luminescence propertie s of Ge island layers deposited by low-pressure chemical vapour deposition was studied. Diode structures containing one Ge island layer were grown sel ectively on patterned wafers with variable area. The analysis shows that th e electroluminescence spectra could be separated into three contributions l ying at low-, medium and high-energy positions, respectively. The absolute peak intensity of each signal depends on the mesa size and on the injected current density. The signal at the low-energy position was assigned to an e ffect due to the facets of the diodes; the two other signals originate from islands on the (001) plane having different Si contents or strain states o n the (001) plane.