The effect of high compressive strain on the operation of AlGaInP quantum-well lasers

In this paper we describe the properties of Ga_xIn_1-xP-(Al_yGa_1-y) _0.52In_0.48P strained quantum-well (QW) lasers at compressive strains of greater than 1%. Structures containing single 100-Å Ga_xIn_1-xP QW´s of different compositions have been grown by low-pressure metal organic chemical vapor deposition (MOCVD) with the intention of studying the physical mechanisms which inhibit the operation of strained lasers at high values of compressive strain. In these lasers, we observe a monotonic increase in threshold current with increasing strain between 1% and 1.7%. We show that the increase in threshold current can be attributed to increased optical losses and we measure an increase in the optical mode loss from 10 to 45 cm^-1 with increasing strain. Using transmission electron microscopy (TEM), we are able to link the increased optical losses at high strain with a strain-induced growth nonuniformity in the active region of the device similar to the Stranski-Krastanov growth mode, which results in the formation of islands in the active region on a 100-nm-length scale