EFFECT OF EXCESS ZN AROUND THE ACTIVE-STRIPE MESA ON THE LASING THRESHOLD CURRENT OF A [011] ORIENTED INGAASP/INP BURIED-HETEROSTRUCTURE LASER-DIODE

Buried-heterostructure lasers with current confinement by;reverse biased junctions always demonstrate poor performance when oriented along the [0 $($) over bar$$ 11] direction of a (100)InP substrate in comparison to the same structure oriented along the [011] direction. We have confirmed that the poor device performance is a result of the excess Zn incorporated in the vicinity of (111)In and (1 $($$$) over bar 11)In mesa sidewall interfaces. The localized enhancement of the Zn level in the first p-InP layer of a standard pnpn current blocking structure is due to the crystal orientation dependent dopant incorporation. The excess Zn precipitates out in the region adjacent to the mesa sidewall interface as observed by cross-sectional transmission electron microscopy. Electroluminescence imaging of active stripe further indicated that the excess Zn diffuses across the sidewall interfaces into the active stripe, generating massive nonradiative recombination centers along the active stripe and degrading the quantum efficiency of the lasers. By systematically reducing the Zn concentration in the mesa sidewall interfacial region, a correlation between an improvement in the lasing threshold current with reduced Zn concentration is demonstrated. A room-temperature threshold current of 10 mA has been achieved in [0 $($) over bar$$ 11] oriented lasers. (C) 1994 American Institute of Physics.