Intervalence band absorption in strained and unstrained InGaAs multiple quantum well structures

Abstract
We report the direct determination of absorption losses in unstrained InGaAs/InGaAsP and InGaAs/InGaAlAs and strained InGaAs/InGaAsP layer multiple quantum well (MQW) laser structures. In the case of the unstrained structures we find a strong dependence of the absorption on carrier density indicating the presence of an intrinsic optical loss mechanism, the intervalence band absorption (IVBA). In the strained layer InGaAs/InGaAsP structures, IVBA is completely switched off. Our results explain the superiority of strained layer InGaAs MQW lasers.