We have investigated barrier width dependence of stacked InGaAs quantum wires, which were naturally formed in a thin InGaAs/AlAs quantum well (QW) with a corrugated AlAs/InGaAs upper interface (a lateral period of about 30 nm and a vertical amplitude of about 1.5nm) and a flat InGaAs/AlAs lower interface. Stacked InGaAs quantum wires (QWRs) separated by a thin AlAs barrier (L-b = 0.5, 1, 2 and 3 nm) were grown on the (7 7 5)B-oriented GaAs substrate by molecular beam epitaxy (MBE). The photoluminescence (PL) peaks from stacked (7 7 5)B InGaAs QWRs with L-b = 0.5 nm were observed at 65 meV lower than that of previous (775)B InGaAs QWR structures. The polarization degree [P drop (I-// - I-perpendicular to)/(I-// - I-perpendicular to)] of PL at 13 K from the (7 7 5)B stacked QWRs with L-b = 0.5 nm is 0.18, which is as large as that of for L-b = 3 nm. The largest PL intensity was shown for the samples with L-b = 0.5 nm. These results indicate that a stack of (7 7 5)B InGaAs QWRs with very thin AlAs barrier layers (L-b = 0.5 nm) are suitable for laser applications due to their larger effective band offset and high polarization degree of PL.