Current spreading modification to enhance single-fundamental-mode VCSEL operation at higher temperatures

Continuous-wave (CW) performance of modern oxide-confined (OC) vertical-cavity surface-emitting diode lasers (VCSELs) at room and elevated temperatures is investigated with the aid of the comprehensive fully self-consistent optical-electrical-thermal-gain model. A standard OC GaInNAs/GaAs double-quantum-well VCSEL emitting the 1.3-μm radiation is used as a typical modern VCSEL structure. The oxide aperture is placed at the anti-node position of an optical standing wave within a VCSEL cavity. The desired single-fundamental-mode (SFM) operation has been found to be expected only in VCSELs equipped with relatively small active regions of diameters equal or smaller than 10 μm. Therefore a proton implantation used as an radial additional confinement of the current spreading from the upper annular contact towards the centrally located active region is proposed and its impact on the VCSEL performance is investigated. The above structure modification has been found to enable a radical improvement in the VCSEL performance. In particular, in this case, the SFM VCSEL operation is possible even in VCSELs with quite large active regions and for much wider ambient-temperature range than in the standard OC VCSELs.