In this work, the In1-yGayAs1-xBix epilayers were optimized and grown successfully by V90 gas source molecular beam epitaxy (GSMBE). The effect of using an In0.53Ga0.47As buffer layer on the crystalline quality of In1-yGayAs1-xBix epilayers were investigated. With the buffer layer preparation, the surface RMS roughness value of 0.251 nm, a maximum electron mobility of 5700 cm(2)/Vs and a bulk carrier density of 2.9 x 10(16) cm(3) are achieved for the In1-yGayAs1-xBix epilayer with the Bi content up to 3.1%. (C) 2017 Elsevier B.V. All rights reserved.