Physics of high-efficiency 240–260 nm deep-ultraviolet lasers and light-emitting diodes on AlGaN substrate

Abstract

High-efficiency III-nitride deep-ultraviolet (DUV) lasers and light-emitting diodes (LEDs) with emission wavelengths of 240–260 nm are extremely difficult to realize due to large defect density from III-nitride materials and existence of optical polarization crossover from conventional AlGaN-based quantum wells (QWs). Free-standing wurtzite AlGaN templates have been studied and developed recently; however, the physics and optical properties of AlGaN-based emitters on AlGaN templates are still relatively lacking. Therefore, this work theoretically investigates the optical properties and quantum efficiencies of the AlGaN-based QW on AlGaN substrates. The physics analysis based on a self-consistent 6-band k⋅p model shows the transverse electric (TE)-polarized optical gain increases from 558 cm−1 by using Al0.51Ga0.49N/AlN QW on the AlN substrate to 2875 cm−1 by using Al0.48Ga0.52N/Al0.72Ga0.28N QW on the Al0.72Ga0.28N substrate at 260 nm, which is attributed to the reduced strain effect and valence band rearrangement by using the AlGaN substrate. Correspondingly, the radiative recombination efficiency increases 1.66–4.43 times based on different Shockley–Read–Hall coefficients, indicating the promising potential of the use of the AlGaN substrate for high-efficiency DUV lasers and LEDs.