Reduction in the series resistance of the distributed Bragg reflector in vertical cavities by using quasi-graded superlattices at the heterointerfaces

Abstract

Surface emitting optical devices with a vertical cavity have been investigated for applications in optical interconnections. To integrate these devices into a two-dimensional array, it is necessary to improve the conversion efficiency from electrical power to optical power. To meet this requirement, the series resistance of the distributed Bragg reflectors that form the vertical cavity must be reduced. This article demonstrates the reduction in the series resistance of the distributed Bragg reflector by introducing quasi-graded superlattices at the heterointerfaces. By using this structure, we obtain a low series resistance distributed Bragg reflector without compromising the high reflectivity. The mechanism of the reduction in the series resistance is studied and it is found that an increase in tunneling current leads to a decrease in the resistance. The dependence of tunneling current on doping concentration of the distributed Bragg reflector and the superlattice structure is also discussed.

Reflectance and Photomodulated Reflectance Studies of Cavity Mode and Excitonic Transitions in an InGaAs/GaAs/AlAs/AlGaAs VCSEL Structure

“…The AlGaAs layers are included to reduce the band offsets at the interfaces, which, together with their high doping, lowers the stack resistivity. Impurity absorption in these layers, since they are thin, does not significantly degrade the high reflectance of the stack [21,22]. For the PR experiments, a standard set-up was used.…”

Dramatically Enhanced Performance of Flexible Micro‐VCSELs via Thermally Engineered Heterogeneous Composite Assemblies

“…Such optical characteristics of microVCSELs are also consistent with the trend in current-voltage curves (Figure 2 c), where the voltage at a fi xed driving current decreases at larger aperture areas due to geometrically and thermally induced reduction of series resistance in the active region and distributed Bragg refl ectors (DBRs), respectively. [ 27,28 ] For measurements of device performance on foreign substrates, micro-VCSELs were released from the source wafer by selective removal of sacrifi cial layer (Al 0.95 Ga 0.05 As) and printed on glass (thickness: ≈1 mm) and PET (thickness: ≈50 µm) using a thin (≈1 µm) layer of photocurable polymer as an organic adhesive. [ 11 ] The maximum output power ( L max ) of micro-VCSELs with an aperture area of 14 × 14 µm 2 was ≈2.4 mW on the source wafer, but substantially decreased to ≈1.0 and ≈0.75 mW when printed on glass and PET, respectively.…”

High-Power Ultralow Divergence Edge-Emitting Diode Laser With Circular Beam

“…The measured series differential resistance R s ≈ 45 mΩ, which gives a resistivity of 16.2 mΩ·mm 2 . The further improvement of the series resistance can be achieved using the bandgap engineering methods to eliminate the band-discontinuity, such as parabolically graded interface [30], delta doping [31], and adding superlattices [32] at the interfaces of DBR.…”