Temperature-enhanced radial current spreading in possible VCSEL structures of nitride lasers

Abstract

A computer simulation based on an advanced self-consistent thermal-electrical finite-element approach has been carried out to analyse electrical and thermal phenomena in possible electrically-biased axially-symmetric annular-contacted nitride VCSELs (vertical-cavity surface-emitting lasers). Joule heating within the upper p-type GaN layer has been determined to be the distinctly dominant heat source in this device. Our analysis revealed that during a continuous-wave (CW) room-temperature (RT) device operation, the highest-temperature area constitutes a ring within the above-mentioned layer close to the active-region perimeter. It dramatically enhances radial current flow from the annular p-side contact towards the centre of the structure before crossing the p-n junction. Therefore current injection into a central active region is considerably improved (by almost 170%!) in RT CW-operating nitride devices as compared with pulse-operating ones. Hence temperature-enhanced radial current spreading within the upper part of the annular-contacted CW nitride VCSELs may enable one to obtain their first RT operation.

Optical isotropization of anisotropic wurtzite Al-rich AlGaN via asymmetric modulation with ultrathin (GaN) m /(AlN) n superlattices

“…For example, the second lowest energy emission with polarization perpendicular to the film plane propagates inside the film and is easily reabsorbed via total reflections, because the photon path length is shorter before the photons escape into the free space. Moreover, the reabsorption within the active region is the most intense heat source, which exerts a deleterious effect on the device .…”