AlGaN-Based Vertical Injection Laser Diodes Using Inverse Tapered p-Waveguide for Efficient Hole Transport

Abstract

An AlGaN deep ultraviolet laser diode design exploiting AlN substrates is presented, featuring an inversetapered p-waveguide layer. The 2-D optoelectronic simulation predicts lasing at 290 nm. Spatial balancing of the lasing mode to minimize optical loss in the p-Ohmic metallization is achieved through the use of a narrow bandgap yet transparent n-waveguide layer. Several electron blocking layer (EBL) designs are investigated and compared with a conventionally tapered EBL design. Through judicious volumetric redistribution of fixed negative polarization charge, inverse tapering may be exploited to achieve nearly flat valence band profiles free from barriers to hole injection into the active region, in contrast to conventional designs. Furthermore, proper selection of quantum well barrier and spacer compositions are demonstrated to reduce electron leakage from the active region. Numerical simulations demonstrate that the inverse tapered strategy is a viable solution for efficient hole injection in deep ultraviolet laser diodes operating at shorter wavelengths (<290 nm).Index Terms-AlN substrate, AlGaN epitaxial layer, deep ultraviolet laser diodes, efficient hole transport, hole blocking layer, inverse tapering, optical absorption loss, polarization charge.

Inverse-Tapered p-Waveguide for Vertical Hole Transport in High-[Al] AlGaN Emitters

“…1 (a). Furthermore, the biggest advantage of the polarization charge is the volumetric redistribution of the fixed negative polarization charge throughout the waveguide which electrostatically attracts the holes toward active region [15]. Another difference between the two valence-band diagrams in Fig.…”

“…Even though the demonstrated high current density shows a potential avenue to realize DUV LDs, the p-SL design leads to a large diode turn-on voltage and this can lead to more serious Joule heating and further limits optical gain. Instead of a p-SL design, we employed an inverse-tapered design, reported by Satter, et al, [15] which allows us to reach a similar current density at a significantly lower voltage as reported in this work.…”

Onset of surface stimulated emission at 260 nm from AlGaN multiple quantum wells

“…[1][2][3][4][5][6][7][8][9][10][11][12] Achieving effective ptype doping in wide-bandgap III-nitride structures becomes a next critical step to realize the DUV laser diodes (LDs) by current injection. 13,14 Bulk AlN and sapphire are two common substrates to grow wide-bandgap AlGaN heterostructures. The materials grown on the sapphire substrates generally suffer from high dislocation density due to large lattice and thermal mismatch in comparison to those grown on the AlN substrates.…”

Simulation of dynamic characteristics of GaN p-i-n avalanche diode operating as particle detector with internal gain

“…Recent advances in semiconductor technology are attained due to intensive investigations and wide applications of gallium nitride (GaN) based semiconductor devices, such as light emitting diodes [1,2] and lasers [3,4], photodiodes [5,6], HEMTs [7,8], surface acoustic wave sensors [9] and acous to-optic devices [10,11]. Gallium nitride is one of the most promising materials for fabrication of particle detectors operating within a harsh radiation environment [12][13][14][15][16][17][18], based on small dark as well as leakage currents and high breakdown voltages.…”