MOCVD-Grown In0.22Ga0.78As Metamorphic Buffer Layer with Ultralow Threading Dislocation Density

Compositional step-graded In0.22Ga0.78As metamorphic buffer layers (MBLs) with a series of thick individual step buffer layers on GaAs substrates are demonstrated by metal organic chemical vapor deposition (MOCVD). The MBL grown at a relatively higher growth temperature (∼750 °C) exhibits a significantly lower threading dislocation density (∼5.0 × 104 cm–2), which is approximately 3 orders of magnitude improvement compared to those grown at 700 °C (∼3.3 × 107cm–2). TEM investigation on an In0.22Ga0.78As cap layer of the MBL suggests no evidence of compositional phase separation. Furthermore, an improved uniformity in photoluminescence across the wafer as well as an improved surface morphology were obtained from the MBL grown with a higher growth temperature.