An attempt has been made to further improve the quality of InxGa1-xAs (x = 0.06) bridge layers on GaAs (1 1 1)B trench substrates by depositing SiNx on the inner surfaces of the trenches. InxGa1-xAs (x = 0.06) layers grown in this way were found to exhibit better quality, as evidenced by microscopic photoluminsecence measurements. The trapezoidal SINx film of large area deposited over the inner surface of the trench was found to be effective in reducing the dislocation content of the bridge layer. The minimum and maximum diameters of the trenches on GaAs(l 1 1)B substrates, keeping other parameters constant, under which the growth of InxGa1-xAs bridge layers is possible have been determined.