The processing technology of 1.3&mgr;m InAs-InGaAs quantum-dot VCSELs with fully doped DBRs grown by MBE will be
demonstrated. The threshold currents of the fabricated devices with 10 &mgr;m oxide-confined aperture are 0.7mA, which
correspond to 890A/cm2 threshold current density. And the threshold voltage of the device is 1.03V and maximum
output power is 33 &mgr;W. The series resistance is 85 &OHgr; which is 10 times lower then our preliminary work and 3 times
lower then intracavity contacted InAs-InGaAs quantum-dot VCSEL. This relatively lower resistance can even comparable with the best result reported in InGaAs oxide-confined VCSELs with intracavity contact.
Proton implanted VCSEL has been demonstrated with good reliability and decent modulation speed up to 1.25 Gb/s.
However, kinks in current vs light output (L-I) has been always an issue in the gain-guided proton implant VCSEL.
The kink related jitter and noise performance made it difficult to meet 2.5 Gb/s (OC-48) requirement. The kinks in
L-I curve can be attributed to non-uniform carrier distribution induced non-uniform gain distribution within emission
area. In this paper, the effects of a Ti/ITO transparent over-coating on the proton-implanted AlGaAs/GaAs VCSELs
(15um diameter aperture) are investigated. The kinks distribution in L-I characteristics from a 2 inch wafer is greatly
improved compared to conventional process. These VCSELs exhibit nearly kink-free L-I output performance with
threshold currents ~3 mA, and the slope efficiencies ~ 0.25 W/A. The near-field emission patterns suggest the
Ti/ITO over-coating facilitates the current spreading and uniform carrier distribution of the top VCSEL contact thus
enhancing the laser performance. Finally, we performed high speed modulation measurement. The eye diagram of
proton-implanted VCSELs with Ti/ITO transparent over-coating operating at 2.125 Gb/s with 10mA bias and 9dB
extinction ratio shows very clean eye with jitter less than 35 ps.
We present in this paper the MOCVD growth and characterization of high performance 850nm InGaAsP/InGaP
strain-compensated MQWs vertical-cavity surface-emitting lasers (VCSELs). These VCSELs exhibit superior
characteristics, with threshold currents ~0.4 mA, and slope efficiencies ~ 0.6 mW/mA. The threshold current change
is less than 0.2 mA and the slope efficiency drops by less than ~30% when the substrate temperature is raised from
room temperature to 85°C. These VCSELs also demonstrate high speed modulation bandwidth up to 12.5Gbit/s from
25°C to 85°C.