Characteristics of step-graded InxGa1−xAs and InGaPySb1−y metamorphic buffer layers on GaAs substrates

Step-graded InGaP_ySb_1-y and In_xGa_1-xAs metamorphic buffer layer (MBL) structures are grown on GaAs substrates by metal-organic chemical vapor deposition (MOCVD). AFM analysis indicates that graded group V InGaP_ySb_1-y MBLs exhibit significantly lower surface roughness (~4.7nm) compared with more conventional graded group III In_xGa_1-xAs MBLs, which typically have rms surface roughness in the range of 7-14nm. To reduce the surface roughness of the In_xGa_1-xAs MBL, a post growth Chemical-Mechanical Polishing (CMP) procedure is implemented. AFM image analysis indicates the CMP process is effective in reducing the step-graded In_xGa_1-xAs MBL surface roughness from ~7.3 nm (as-grown) to 2.3 nm post CMP. Preliminary studies indicate that bulk InGaAs layers regrown on top of the MBL subjected to CMP exhibit improved static and transient PL characteristics compared with those deposited on as-grown MBLs.