Growth and characterization of MO/VPE double-heterojunction lasers

Metalorganic vapor-phase epitaxy (MO/VPE) has been used for the growth and fabrication of double-heterojunction (DH) devices. Al0.3Ga0.7As/GaAs DH mesa stripe lasers were made, which have a threshold current density of 6.7 kA/cm². We attribute this high value to recombination losses at killer centers situated in the confinement layers very close to the active layer; it is shown that these killers were introduced by using dopant concentrations beyond cm^-3. The MO/VPE technique was also applied for burying mesa lasers. The threshold current density of an LPE mesa buried with monocrystalline (Al, Ga)As was 3.5 kA/cm²; i.e., 60 percent higher than its corresponding broad-area value. It is shown that in order to reduce the excess current, the recombination velocity at the VPE/LPE active-layer interfaces should be lowered; viz., to a value below the diffusion velocity of carriers towards these interfaces. The optical mode structure of the buried mesa (BM) lasers was stable up to a power output of 10 mW/facet.