Internal loss of AlGaN-based ultraviolet-B band laser diodes with p-type AlGaN cladding layer using polarization doping

Aluminum gallium nitride (AlGaN)-based ultraviolet-B band laser diodes (LDs) with a p-type AlGaN cladding layer using polarization doping were fabricated on lattice-relaxed Al0.6Ga0.4N/AlN/sapphire. The threshold current density Jth and lasing wavelength of this LD were 25 kA cm−2 and 298 nm, respectively. The internal loss (αi) was estimated by means of a variable stripe length method using optical excitation. The αi value of this LD was relatively low (i.e. <10 cm−1), thus suggesting that the device is characterized by both, proper light confinement and low internal loss.