Effect of strain relaxation layers in high Indium content metamorphic InGaAs/InAlAs modulation doped heterostructures

We have investigated effect of residual strain appeared in the transport and optical properties of high indium content metamorphic In/sub 0.75/Ga/sub 0.25/As/In/sub 0.75/Al/sub 0.25/As modulation doped heterostructures grown via (inverse step: IS-) step graded buffer (SGB). The effect of residual strain was controlled by IS structure and a drastic decrease of residual strain (about one third) was observed. We have also observed an improved low temperature (77 K) electron mobility, when the IS buffer was used. We found that the residual strain is one of the important interface condition which determines the low temperature (77 K) electron mobility.