Low-threshold stimulated emission at 249 nm and 256 nm from AlGaN-based multiple-quantum-well lasers grown on sapphire substrates

Abstract

Optically pumped deep-ultraviolet (DUV) lasing with low threshold was demonstrated from AlGaN-based multiple-quantum-well (MQW) heterostructures grown on sapphire substrates. The epitaxial layers were grown pseudomorphically by metalorganic chemical vapor deposition on (0001) sapphire substrates. Stimulated emission was observed at wavelengths of 256 nm and 249 nm with thresholds of 61 kW/cm2 and 95 kW/cm2 at room temperature, respectively. The thresholds are comparable to the reported state-of-the-art AlGaN-based MQW DUV lasers grown on bulk AlN substrates emitting at 266 nm. These low thresholds are attributed to the optimization of active region and waveguide layer as well as the use of high-quality AlN/sapphire templates. The stimulated emission above threshold was dominated by transverse-electric polarization. This work demonstrates the potential candidacy of sapphire substrates for DUV diode lasers.

Molecular beam epitaxy growth of Al-rich AlGaN nanowires for deep ultraviolet optoelectronics

“…AlGaN compound semiconductors, with their wide optical bandgap tunability from 200 to 364 nm, have been intensively investigated for applications in UV LEDs and lasers. [1][2][3][4][5][6][7][8][9][10][11][12][13] However, compared to the well-established high performance GaN-based quantum well LEDs and lasers operating in the near-UV, blue, and blue-green spectral ranges, realizing high performance AlGaN quantum well UV LEDs and lasers in the UV-C band (200-280 nm), in particular those emitting below 240 nm, has been extremely challenging. [1][2][3][4][13][14][15][16][17] The extraordinary challenges include the presence of large dislocation and defect densities, the extremely inefficient p-type conduction due to the large Mg activation energy and doping induced defect donors, and the unique TM light polarization in Al-rich AlGaN.…”

Recent Progress in AlGaN Deep-UV LEDs

“…University of Berlin recently carried out a series of studies on the properties of AlGaN epilayers and AlGaN and InAlGaN UV LEDs [2,[43][44][45]. The reported EQEs for AlGaN and InAlGaN UVA-UVC LEDs up to 2015 are summarized in Figure 1.1 of Ref.…”

MOVPE Growth of Smooth and Homogeneous Al0.8Ga0.2N:Si Superlattices as UVC Laser Cladding Layers

“…However, no AlGaN‐based quantum well LD emitting in the deep UV spectral region has been reported yet. Up to now, electrically driven laser diodes emitting in the UVA spectral range have been demonstrated as well as low threshold optically pumped UVC lasers . Key challenges for the realization of electrically driven deep UV LDs are low resistance Si‐ and Mg‐doped AlGaN cladding and waveguide layers, efficient carrier injection into the AlGaN quantum well active region, as well as strong transversal optical mode confinement and low loss cavities.…”