Strain relaxation in In0.2Ga0.8As/GaAs MQW structures

We study the limits of pseudomorphic strain in MBE grown In0.2Ga0.8As/GaAs multiple quantum well structures and the influence of lattice relaxation on the optoelectronic properties of high-speed p-i-n photodetectors with MQWs in the intrinsic region. High-resolution X-ray diffraction yields the degree of lattice relaxation. For the detectors these results are in agreement with photocurrent spectroscopy measurements and subband calculations. The detectors yield a quantum efficiency of unity, in spite of the onset of lattice relaxation.