Demonstration of transverse-magnetic deep-ultraviolet stimulated emission from AlGaN multiple-quantum-well lasers grown on a sapphire substrate

Abstract

We demonstrate transverse-magnetic (TM) dominant deep-ultraviolet (DUV) stimulated emission from photo-pumped AlGaN multiple-quantum-well lasers grown pseudomorphically on an AlN/sapphire template by means of photoluminescence at room temperature. The TM-dominant stimulated emission was observed at wavelengths of 239, 242, and 243 nm with low thresholds of 280, 250, and 290 kW/cm2, respectively. In particular, the lasing wavelength of 239 nm is shorter compared to other reports for AlGaN lasers grown on foreign substrates including sapphire and SiC. The peak wavelength difference between the transverse-electric (TE)-polarized emission and TM-polarized emission was approximately zero for the lasers in this study, indicating the crossover of crystal-field split-off hole and heavy-hole valence bands. The rapid variation of polarization between TE- and TM-dominance versus the change in lasing wavelength from 243 to 249 nm can be attributed to a dramatic change in the TE-to-TM gain coefficient ratio for the sapphire-based DUV lasers in the vicinity of TE-TM switch.

Optical Quality and Stimulated Emission of Molecular Beam Epitaxy Grown AlGaN in the Deep Ultraviolet

“…[ 9–11 ] In contrast, however, the development of AlGaN‐based deep UV lasers is much slower, and the majority studies focus on optically pumped AlGaN QW lasers. [ 12–17 ] It is not until very recently that the electrically pumped AlGaN QW deep UV laser operating at 271.8 nm was achieved, [ 18 ] after the clamping of the lasing wavelength at 336 nm for more than one decade. [ 19,20 ]…”

100‐nm thick single‐phase wurtzite BAlN films with boron contents over 10%

“…Due to the direct and appropriate bandgap energy, III‐nitrides are suitable semiconductor materials for DUV lasers. Recently, low‐threshold optically pumped edge‐emitting lasers based on III‐nitrides have been demonstrated, which is an important milestone towards realization of electrical‐driven edge‐emitting laser diodes .…”

Physics and polarization characteristics of 298 nm AlN-delta-GaN quantum well ultraviolet light-emitting diodes

“…[4][5][6][7][8][9] This extremely low g EQE can mainly be attributed to the material challenges including high dislocation densities (10 10 cm À2 in AlN and AlGaN layers) 10,11 and relatively low electrical conductivity in p-and n-type AlGaN cladding layers, [12][13][14][15][16][17] as well as the physics challenges such as a severe valence band-mixing effect in conventional AlGaN QW structures. [18][19][20][21][22] Specifically, previous studies revealed that the crystalfield split-off (CH) subband is dominant in the valence band for high Al-content (>68%) AlGaN QWs, which results in dominant transverse-magnetic (TM)-polarized emission at k $ 220-230 nm. 18 However, with the decrease in the Al-content, the heavy hole (HH) subband gradually moves toward the highest energy level in the valence band and causes the corresponding transition from the conduction band to the heavy hole subband (C-HH) to mix with C-light hole (LH) and C-CH transitions at k $250-300 nm.…”