Influence of the mesa size on Ge island electroluminescence properties

The influence of the mesa size on the structural and luminescence properties of Ge island layers deposited by low-pressure chemical vapour deposition was studied. Diode structures containing one Ge island layer were grown selectively on patterned wafers with variable area. The analysis shows that the electroluminescence spectra could be separated into three contributions lying 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 effect 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 on the (001) plane