Threshold currents of nitride vertical-cavity surface-emitting lasers with various active regions
Pawel Mackowiak, Wlodzimierz Nakwaski
Institute of Physics, Technical University of Lódz
This article was received on Thursday, June 18, 1998 and
accepted on Wednesday, October 7, 1998. Abstract
A
detailed threshold analysis of room-temperature pulsed operation of
GaN/AlGaN/AlN vertical-cavity surface-emitting lasers (VCSELs) is carried out.
The model takes advantage of the latest results concerning gain in active
regions, material absorption in the cladding layers, as well as cavity
diffraction and scattering losses. The simulation showed that although VCSELs
with single (S) or multiple (M) quantum-well (QW) active regions exhibit lower
threshold currents, they are much more sensitive to any increase in optical
losses than their bulk counterparts. In particular, decreasing the active
region radius of gain-guided QW VCSELs below 5 µm (which increases
diffraction losses) or increasing dislocation densities (which, in turn, raises
scattering losses) gives an enormous rise to their threshold currents.
Therefore small-size GaN VCSELs should have an index-guided structure. In the
case of MQW VCSELs, the optimal number of quantum wells strongly depends on the
reflectivities of resonator mirrors. According to our study, MQW GaN lasers
usually require noticeably lower threshold currents compared to SQW lasers. The
optimal number of QW active layers is lower in laser structures exhibiting
lower optical losses. Although the best result occurred for an active region
thickness of 4 nm, threshold currents for the various sizes differ
insignificantly.
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Cite this article as: MRS Internet J. Nitride Semicond. Res. 3, 35(1998).
last updated Monday, October 26, 1998 9:52:52 AM.© 1998 The Materials Research Society
