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.

In this study, we employed bulk (0001) AlN substrates for the metalorganic chemical vapor deposition growth of AlGaN multi‐quantum‐well heterostructures in an Aixtron 6 × 2″ close‐coupled showerhead reactor. The wafers were fabricated into cleaved bars with a cavity length of ∼1 mm. Two different layer structure designs are presented in this work. Both laser bars were optically pumped by a pulsed 193 nm ArF excimer laser at room temperature. The lasing wavelengths are 243.5 nm and 245.3 nm with threshold power density 427 kW/cm2 and 297 kW/cm2, respectively. Both laser bars showed transverse electric‐polarization‐dominated optical emission when operating above threshold. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We report a high-aluminum-containing ([Al] ∼ 0.6) AlGaN multiple-quantum well (MQW) doubleheterojunction (DH) emitter employing an inverse-taperedcomposition AlGaN:Mg p-type waveguide grown on a c plane Al-polar AlN bulk substrate. Using numerical simulations, we have determined that the inverse-tapered p-type waveguide design is necessary for high [Al] containing p-n junction devices as any valence band discontinuity at the junction will limit the vertical hole transport and induce a larger voltage-drop across the structure. The fabricated ultraviolet MQW DH emitter can sustain a DC current of at least 500 mA and a pulsed current of at least 1.07 A, which corresponds to a current density of 10 and 18 kA/cm 2 at maximum measured voltage of 15 and 20 V with the measured series resistance of 15 and 11 , respectively.Index Terms-AlN substrate, AlGaN active layer, epitaxial growth, deep ultraviolet laser diodes.