Photoluminescence excitation spectroscopy of InAs_0.67P_0.33/InP strained single quantum wells

The optical emission characteristics of biaxially compressed InAs_xP_1-x/InP strained single quantum well (QW) structures, with nominal composition x=0.67, have been investigated using photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. The highly strained QWs exhibit intense and narrow PL in the 0.9-1.5 μm wavelength range, similar to the lattice-matched InGaAs(P)/InP system. The 20 K PLE spectra exhibit well-resolved features attributed to n=1 heavy hole (E1H1) and light hole (E1L1) transitions in the 1.0-1.5 μm wavelength range. In addition, features attributed to transitions between n=2 electrons and heavy holes (E2H2), and between n=1 electrons and unconfined holes (E1Hf), were observed. The energy splitting between the heavy-hole and light-hole bands was found to be a sensitive measure of the band offsets in the system. The best prediction of this splitting was obtained for a valence band offset of δE_V∼0.25δE_G. This value of band offset was in agreement with the energy position of the E1Hf transition. The observed transition energies were also compared with the results of a finite square well model, taking into account the effects of strain, and the results offer further support for the band offset assignment. This study indicates that the InAsP system may be advantageous for application in strained-layer optoelectronic devices operating in the 1.3-1.6 μm wavelength range.