Current spreading and series resistance in proton-implanted top-surface-emitting lasers

Proton-implanted top-surface-emitting lasers (PITSELs) are known to exhibit relatively high electrical series resistances. Initially, these were attributed to the high series resistance of p-type Bragg mirrors with abrupt interfaces. However, even in the case of devices with stepped, graded-superlattice, linearly graded or sinusoidally graded mirrors, the series resistance still remains high in comparison to common stripe-geometry lasers. Recently, we have obtained analytical solutions for spreading resistance in the top section of surface-emitting lasers, assuming a uniform current