Optimization of Carrier Distributions in Periodic Gain Structures toward Blue VCSELs

Abstract

We have fabricated light emitting diodes (LEDs) in which two active regions separated with a Mg-doped GaN intermediate layer were placed in a single pn junction toward periodic gain structures (PGS) for blue vertical-cavity surface emitting lasers (VCSELs). By current density dependence on a emission intensity ratio from two different active regions, we obtained a very stable emission intensity ratio over 1 kA/cm2. This result is also confirmed with the simulation result. Furthermore, we found that the difference of emission wavelength affect the carrier injection and the emission intensity ratio. On the basis of this result, the optimized well-balanced Mg concentration in the intermediate layer for the two identical active regions were estimated approximately 5 x 1018 cm-3.

Electron and hole accumulations at GaN/AlInN/GaN interfaces and conductive n-type AlInN/GaN distributed Bragg reflectors

“…The above results suggest that the layer with high Si doping is more effective than the graded layer to obtain the conductive n-type AlInN=GaN DBRs, meaning that the impact of the polarization charges on the electrical properties is huge in nitride-based materials. So far, laser operations of nitride-based vertical cavity surface emitting lasers (VCSELs) with undoped AlInN=GaN DBRs were reported, [25][26][27] and the undoped DBRs were not conductive at all, so that intracavity contacts must be used, resulting in high resistance and internal loss. As a result, such a conductive nitride-based DBR will lead to high-performance blue VCSELs, like the already commercialized infrared VCSELs with the conductive DBRs.…”

In situ wafer curvature measurement and strain control of AlInN/GaN distributed Bragg reflectors

“…[1][2][3] Recently, lasing operations of GaN-based VCSELs with bottom AlInN/GaN distributed Bragg reflectors (DBRs) from violet to blue regions have been reported. [4][5][6][7][8][9][10][11][12][13][14] In this case, it is indispensable to control the InN mole fraction of the AlInN layers to be lattice-matched to the GaN layers in the several μm epitaxial DBRs.…”