A 25 period InAs0.54P0.46/In0.89Ga 0.11P MQW for 1.55 μm modulation grown by solid source MBE

A 25 period multi-quantum well containing 83 nm wells of InAs_0.54P_0.45 and 10.7 nm barriers of In_0.89 Ga_0.41P has been grown by solid source MBE. Despite the 1.8% strain in the wells, -0.8% barrier strain and a net strain in the 0.48 μm stack of 0.3% (compressive) there is no evidence of any strain relaxation. Both (004) and (115) X-ray spectra were measured to confirm the lattice constant in the plane was that of InP. The similar well and barrier thicknesses in the 25 period structure combined with complete strain accommodation imply excellent prospects for achieving a 1.55 μm normal incidence modulator with a large number of periods and hence high contrast ratio. Unfortunately, despite the structural integrity of this device, optical modulation could not be demonstrated at room temperature due to high doping in the intrinsic region (mid-10 ¹⁶ cm^-3). However, a lower-doped 5 period structure showed a strong quantum confined Stark effect with persistence of the exciton up to 320 kV/cm. The change in absorption at 1550 nm was 7,300 cm^-1 per well at 160 kV/cm. Similar absorption characteristics in the 25 period structure would result in modulation of 3,200 cm^-1, which is comparable with InGaAs[P]/InP at the same wavelength